Ok, I'm using mx4 since KitKat. I don't remember this problem on KitKat, but when I've updated Flyme from 4.5.7I to 5.1.5.0A, I saw an interesting "bug" with swipes from top to botton and in reverse way. I attach a gif-file to show you.
So, in a few words: when i'm swiping to unlock the phone, in 70% of all cases, it's all OK, but in other 30% any application (in video it is Adobe reader) from home screen can start with the swipe. Also, if you start, for exapmple, phone application, then turn off the screen, and then make swipe to unlock, this swipe can also "touch" any contact nearby, and the fake "calling" will begin.
It's all the same about swipe from top to botton. You make swipe, and with this swipe any button in blinds can be activated/deactivated, for example, sometimes I make a swipe, and this swipe turns off DND mode or turns on GRS.

I made upgradings with factory reset, made factory resets, and I dons use "letters-swipes", so, I don't know, where to find problem.
This probles was from 5.1.5.0A to 5.1.11.1A and even on flyme6 (6.6.12.30) this problem is still existing.
Thank you.