I crashed my APEX4 the other week, on starting it up in acro it ticks over fine until you give it some power then it flips out…
Same if you start it in Horizon mode due to the higher prop spin it flips out straight away. Iv given it a good look over and cant see anything obvious everything seems as it should.
I was wounding if anyone has come across this before…
Are all props rotating or just 3 (or less) ?
Are motors appearing to be at the same strength?
In angle mode, when you hold it ‘carefully’ can you feel it trying to stabilise when you move/angle your hand or is all he force always in one direction?
Any motor getting hot?
Any ESC getting hot?
Sounds like loose props to me.
It sounds very familiar. I’m sure someone else on here had the same issue a few months back. Can’t recall who though.
Motor spinning the wrong way or the wrong prop(s) on?
I had lose props today on one motor and you could hear it though could tell under low throttle as well as high.
Also crashed a bit 
No iv changed them all as a couple were bent, and double checked there on the right way
Yep there all rotating 
as for same strength that’s an interesting idea …will check
Motors all seem intact not a scratch on them, ill do a bit more investigating and get back to you …
I’d check each one if betaflight to see if they match up
That was my next port of call, Im on a bloody course next week so may take it with me and do some investigating back in my room 