Hey there folks!
Good news - the bug has finally been resolved! 

I expect y’all have already seen the email update on this that was sent out but if not, here’s the details that were shared on that update:
“We've resolved the issue some users were encountering while creating company updates on Showcase (Brand) pages. We've made necessary adjustments to ensure a smooth experience when creating updates on Showcase pages. Now, the process should proceed seamlessly without any hitches. This improvement has been automatically applied, so there's no action required on your part. Feel free to resume using this feature if you had held off due to this issue! Should you have any further questions or run into any other issues, we’re here to help.”
Happy Zapping! 
Hi folks! 
@Volo Nuke and @tfell99 I’ve added you both to the list of affected users which does help to increase it’s priority. When it comes to prioritising issues, we take into consideration several factors like the number of folks affected, complexity of the fix and severity of the issue. While I can’t provide any sort of estimate as to when this issue may be resolved by we’ll definitely notify you by email the minute it’s solved.
I did see some details noted that mentioned these errors were sometimes occurring due to issues with the permissions for the connected LinkedIn account. So I’d recommend checking that the connected account has the correct admin permissions for the page the update is being posted to. From what I can see on the LinkedIn website, it looks like there’s two kinds of admin roles available - Super Admin and Content Admin (LinkedIn Page admin roles permissions). And only Super Admin appears to have the ability to “Create Showcase Pages” so I’m thinking that perhaps you’d need to have Super Admin permissions in order to post an update to a showcase page.
Is anyone here able to confirm whether they’ve got Super Admin permissions and are still seeing that error?
@tfell99 - this thread was opened for an error with the LinkedIn app specifically, not Youtube. Are you running into an issue with the New Video in Playlist trigger? If so, can you confirm what error you’re seeing? If you can share a screenshot showing the full error message you’re seeing that would be much appreciated. Please remove/hide any private information from the screenshot before sharing (like names, email addresses etc.).
Thanks, I’ll be keeping an eye out for a response here! 
Same problem encountered here. Suprised no solution after 3 years. Just remove the Youtube playlist feature.
It is frustrating but now I’ll find another way around it.
This BUG has been around for more than three years and you still haven't solved it. To me it seems like a mockery of your customers to keep saying you're working on it. If you don't intend to solve the problem seriously and in a acceptable deadlines, simply say so, so that your customers will organize their work process differently. We are paying Zapier to solve our problems, not to create them.
Hi @EvaVogel
I’ve added you to the list of affected user and we’ll send you an email regarding with an update for this bug. Thanks!
Hey Zapier Team,
We also run into this error. Please add me to the list of affected users.
This error isr really annoying and should really be solved soon ...
Thanks!
Hi @MediaTrend
I’ve added you to the list of affected users. We’ll update you via email once available. Thanks!
Can you please add me on to the list of all impacted users and keep us notified?
And how about giving this issue some priority in stead of apologising, it has been open for 2 years already. Other platforms manage to do this. We are a paying customer and this should be a standard feature.
Now we still have to use Buffer next to Zapier to do basic LinkedIn showcase posts. Or is there any way to get compensation?
Thanks!
Hi @meonvalleytravel
We do apologize for any delays.
We don’t have any updates yet, but I’ve added you to the list of affected users, and we’ll update you via email once there are any changes. Thanks!
Hi,
Any update on this issue? Can you give us a timeline on when it will be fixed?
Can you add me on to the list of impacted users?
Thanks,
JD
Hi there, @POSITIVR! I’m sorry for the delay on this.
While we don’t have any updates to share at the moment, I did get you added to the list of impacted users. We’ll be sure to send an email as soon as we know more!
Hey Zapier Team,
We also run into this error.
Any news about this ?
Here is the error : “Field Value validation failed in REQUEST_BODY: Data Processing Exception while processing fields [/author]”
Thanks for sharing this info with us, @Meinie. We’ll be sure to let you know as soon as it’s working again. Fingers crossed it’ll be sorted soon! :)
Hello. Thank you very much. In our case Zapier was able to create company updates on LinkedIn showcase pages until mid of july. Since then the error message mentioned above appears and zapier stopped posting on those pages. True company pages still work, but showcase pages do not.
Hi there, @Meinie.
Welcome to the community!
Thanks for reaching out and letting us know. I’ve gotten you added to the report as an affected user. We’ll keep you updated via email as soon as we have a fix in place.
Hi!
We do have the same problem as well.
No, I need the showcase page. I don't understand why other apps can handle this easily but zapier has an issue for more than a year?
Really glad to hear you were able to get a temporary, workaround in place here, @marycanady. We’ll definitely let you know as soon as it’s been fixed.
Paying for both definitely isn’t ideal and I’m not sure if this would be a good option for you, but do you have an account using a standard company page, not a showcase page? If so, you should be able to use that LinkedIn account instead in the Zap without running into that error. Hope that helps! :)
Thanks @christina.d I did confirm via Twitter that Hootsuite no longer supports RSS. I found a solution to use Buffer and Zapier, but I’m not thrilled about paying for both. I hope Zapier can fix the problem.
Thanks so much for reaching out, @marycanady! While we don’t have an update at this time, I’ve gone ahead and added you to the list of impacted users. We’ll send you an email and be sure to keep this thread updated as soon as we know more!
Bumping this up as well. Hootsuite just turned off their RSS to LinkedIn company showcase page support (I think) and so you’ll have more users wanting this. Any updates?
Welcome to the Community, @kgv!
I’m so sorry to hear you’re running into this issue, and on your very first Zap too! :(
I’ve added you to the list of affected users as well. I don’t have an ETA but we’ll reach out to you by email as soon as this gets resolved. :)
Unfortunately I seem to be affected by the exact issue listed above. Not great with it being the first “Zap” I tried to set up.
Hi @alangan!
I’ve added you to the list of affected users!
@Liz_Roberts I am having the exact same issue--can I be added as an impacted user as well? TIA