Do you have the issue only with that project or is it with all your projects?
I had that problem in 7.23.X as well.
It seems to be local-ish since only I and one other person had it with our project.
It also seems to depend on how many commits you have and are trying to merge. I have had luck with merging them 1 or 2 commits at a time to another branch to then do 1 commit, kind of a git squash. And then merging the one commit from the new branch.
But in general, since this is some kind of time out with svn and mendix servers, one seems to be screwed.
The easy solution is to use another computer.