Error when making updates to existing advanced create - premium function apps

[MicroFish91]

We are seeing this error appearing throughout whenever we try to update an existing Advanced Create - Premium Function App.
(Other types may be affected too)

I've gone way back to older commits to test this out and I'm seeing this same problem appearing, even on super common update calls to change app settings. This makes me think that it could be an external issue and not necessarily an internal regression (would appreciate anyone else who has time to help confirm this though).

The commands affected are basically any commands that try to update an existing Function App.

Here is a common example of an update SDK call that will now trigger this weird error for certain Function Apps:

More information on my initial investigation findings: https://github.com/microsoft/vscode-azurefunctions/issues/4845#issuecomment-3604873278