Thanks for your post.
The last time this happened, it was something to do with a linked server pointing back to the same database. That's sort of hard to troubleshoot, but I think if you enable verbose logging you should be able to get the name of the object causing the problem and we can work from there.
1. add /LogLevel:verbose to the command.
2. check %userprofile%\\appdata\\local\\red gate\\logs\\sql compare 10 for the most recent log file.
you could try adding /transactionIsolationLevel:"READ COMMITTED" and see if that helps. This runs the schema update without exclusive locks, which is dangerous from a consistency point-of-view, but may get the update working.