Are their problems syncing program folder inside folder share?

I’m guessing I know the answer to this question but wanted to make sure.

Would there be problems if the Syncthing folder is within the folder share that is synced to other devices?

I have 3 separate Syncthing folders (1 for each device) so they are not all running the same instance, but I do like to sync the folders to the other device so syncthing is backed up with the rest of data.

What is “the Syncthing folder”? If you are talking about the folder that stores the database, then yes, you are most likely to corrupt everything.