Can you please write when does exactly freeze and reboot? After installing an app/restoring backup?
I flashed the latest sMiUI on a clean install and everything is fine, i'm writing this through 5.3.13 and everything is fine..
Aroma with all option on
Bootlog
aroma log
I am able to confirm this, colors are strange on the latest versions, i noticed it in games and i am 101% sure that some backgrounds weren't shown like this!
I think it's miui fault this time...
Don't reboot lol
btw, doesn't always matter on the free space. Did you checked your /system partition? May be a dirty flash?
I can't really help you with any more accurate description/information..
For example, one cause of reboot for me was full /system partition (with 32gb free on /sdcard)...