Atom adds syntax on save

Hi - I’ve been using Atom for a while.
I’ve recently changed to using a separate local machine for dev (XAMPP) and mounting it as an OSX volume, then opening/editing files on main machine either via a Project folder or using Finder GUI.

For some reason (seemingly randomly) upon save Atom is injecting syntax into the saved file (it appears as I save). The file shows as saved and is changed on the remote machine. Restating in safe mode hasn’t made a difference. Fresh re-start of both machines doesn’t stop the issue.

Editing directly on the remote machine (using Atom or TextEdit) works as expected. After saving locally the ‘injecting’ appears to stop but later returns.

I assume this is somehow cache related but I do not know if Atom has a cache nor where to start to debug.

Any help appreciated!