@sz If you meant PRO5 , read here those links, should help you. If you meant MX5 , this device was never supported, so no such a thing as UT on it.
The most likely your problem is ,,too small cache partition,, (Meizu Pro 5 )
https://forums.ubports.com/topic/665/meizu-pro-5-without-any-os
https://forums.ubports.com/topic/1610/meizu-pro-5-16-04-stable-backup-for-restoring-with-twrp
https://forums.ubports.com/topic/1252/problems-flashing-ubports-on-meizu-pro-5-android-international-edition
http://sturmflut.github.io/