MS 4 removed nearly all my slurs

Hello

Strange problem with MS4.1.1 I haven't encountered before. I have a piece I'm engraving for string quartet (4 staves) and when I opened my most recent revision, I noticed nearly all the slurs were missing from all four staves. I don't know exactly when or how this happened.

So, I was a bit frustrated, but having never seen this before I assumed it was a one-off and I re-entered all the slurs in the score in a new revision and everything looked great. I opened the individual parts and these looked fine. When I reopened the file at a later time, I noticed the slurs were gone again in 3 of the staves, but this time the cello slurs remained. I noticed the parts are just fine and contain all the slurs, so they were only deleted from the score.

Here's the only clues I can find:
1. Possibly happens on file open or close (I'm not sure of this, but I didn't observe it happening when I was working on the file).
2. Doesn't seem to delete the slurs in the individual parts.
2. It seems to keep the slurs when there is a tie inside the slur (see picture).
3. Doesn't happen with ties, only slurs.

I have no idea how this happened, nor how to recreate it.

Before I log a bug in GitHub I wanted to see if anyone else has had this problem or if it's a known issue. I will upload my file revisions to the bug report. I wish I could recreate this - I guess maybe it's possible that my file got corrupted somehow (since I've not seen this before), but that shouldn't happen anyhow, or at the program should report the file is corrupted.

Thanks for any insights. This is a very frustrating problem and means a lot of rework if this happens to folks.