I am not experiencing these issues you are having with Android 7. My box is stable and apart from a few known quirks I am generally happy with it.
Although this is not a long-term solution for you, I would suggest running a stock standard version for a while, to see if you still have the same issues you are currently getting. With Kodi being the exception, I would recommend Kodi 17.6 (shitty) version. I am running this version with only an occasional hiccup. Sometimes when I start Kodi, I get a message it is not responding, exiting out and restarting Kodi works the next time.
It might be one particular app that is causing you grief and the only way to find out will be process of elimination.
I might also add; I would lay off installing lots of Kodi plug-ins until you are satisfied you have a stable base.
Are the crashes and slowdowns in general usage on the Q10 or do they happen while using Kodi?
As a trial run, if you went to Android 7 with the latest firmware and no other packages (apart from kodi update) installed, is the outcome still the same?