Hi,
with every update (20.0.4 at the moment) I have the same problem. Stuck in step5, but there is no error given (field is empty). My virtual server has not very much PHP memory (128 MB), so maybe this is the problem, but this is only a guess, since no error message is given.
After some manual updates, I find it most convenient to skip the verification by chnanging the .steps file to:
{"state":"end","step":5}
However, I always have a bad feeling, fearing that the update ultimately might fail and I have to set up the whole thing from scratch.
It would be nice if the dev team got a look into this problem.
Regards