Master slide transparency changing when copying from server

Hello,

We create/update hundreds of storyline 360 courses every year. We work locally, but then upload our source files to a server for retention. When making any edits/updates, we copy the story files back to our local computers to work.

Every time I copy a story file from our server to my local computer, the background on the slide master changes to 100% transparency (we want them set to white, 0% transparency). This happens all the time, even on files I worked on a week previously. As soon as I copy it to the server and then back, I need to go back to my slide layers and fix the transparency.

Does this happen to anyone else? Is there a project setting over-riding my masters somewhere? I am not new to articulate; I have been using storyline almost daily since SL1 around 2010,2011. I believe this started when we switched from SL3 to SL 360.

Thanks for any help/advice.

Cyndy