Something went wrong during merge


All our merge requests on a particular repository are failing when we’re clicking the Merge button to get GitLab to do them automatically.

After clicking Merge, we see the message “Something went wrong during merge”. There are no other messages.

In production.log, I get an extra bit of detail:
MergeService ERROR: core/server!9 - can’t modify frozen String

Has anybody got any bright ideas? would be most appreciated.

We can still do merges, but they have to be manual.