[Renate]

Well, if you're data isn't valuable you can try the factory reset.

When the device boots it looks to see if there is any unmerged updates.
If there are it tries to merge them.
I don't think that you mentioned that there was any delay in starting all the previous times.
It appears that by getting rid of the snapshots in metadata that at least that seems to have improved.
There could be corruptions/problems in /data preventing it from starting the normal system.
I still don't understand this 11% business.
If it was well written it would finish (with errors) and not stall no matter what the problem was.