So I'm not sure if this will help - it's hard to diagnose this without seeing it occur. I would, however, point you to this discussion:
The first issue described here sounds like the same as yours - error message of missing fields after an action. The solution was that the field for the action was not in both views, it sounds like. Hopefully this is similar and/or will fix your issue?
Otherwise, is there any way to recreate this error you see in a sample workbook? I'm guessing this will be really hard to answer for anyone without seeing the error come up. I'm sure your original data is sensitive so I understand if this can't be done. Though sometimes I find a solution just trying to recreate the error.
Though on a personal note, it'd be great to see this in a sample workbook, because I'd love to see how you did this:
for that report, i implemented two action features that took the product ID as a variable and executed a URL that used that product ID as an input.
as you said so yourself, the data is confidential so i cannot share it.
same goes with the URL since it addresses an internal search node.
any way, i figured the issue out already but i believe this should be reported as a bug (but i dont know how).
when using a data source that was previously loaded to the Tableau server, if we try to create a URL action we will get an alert for a missing field even if the field name was selected from a drop down list of field names originated in the data source.
if we leave it this way and load the dashboard to the server, the action item starts working perfect.
the bug is that when developing with the tableau desktop, the action seems to be not working even if it is actually OK.
regarding your question, if you need any specific help with you data, let me know and i'll try to help as much as i can...