After looking at your flow again, I don't know how it could be working in the first place.
The first apply to each "Apply to each 2" is based on a SharePoint get files step. So for each file it will do actions within "Apply to each 2".
The second apply to each "Apply to each" is trying to say, "For each individual file in Apply to each 2, I would like to get each Identifier for that individual file. The do actions to each one of those identifiers."
That doesn't make sense. Each file only has 1 identifier, it doesn't have a list of identifiers.
I made an example and mine failed because it can't apply to each on an identifer.
Example Apply to Each
Example Apply to Each Failed
So I don't know how this flow was working at all for months. It doesn't work once. I can only guess it never had any files that were 180 days old, so it never got any further than the first "Apply to each 2" because it was always empty. So the second "Apply to each" never got a chance to run and create an error.
You should get rid of that nested apply to each and you only need one.
Delete a File
This example should work correctly. Let me know if this works for you.
