so this has been happening for a few weeks now and i cant figure it out. been running this build for about 6 months no issues and then randomly started losing motors mid flight ? not electrically, like the actual screws are vibrating loose. happened twice now and once i nearly lost the quad in a tree because it just went sideways out of nowhere.

im using the stock screws that came with the motors (BrotherHobby Returner R5s) and the frame is a TBS Source One. already tried tightening them down hard but it keeps happening. someone mentioned threadlocker but i heard you can use the wrong kind and then you can never get the motor off again. is blue loctite actually safe for this or what do people usually do

also wondering if its a vibration problem rather than just the screws, like maybe my props are unbalanced or something. one of them did take a pretty good hit a few weeks ago and i just kept flying it

blue loctite is fine, that's what basically everyone uses. red is the permanent stuff, dont touch that for anything you ever want to remove. blue will hold the screws but you can still get them out with a driver if you need to, sometimes takes a bit of heat but nothing crazy. just put a tiny drop on each screw, not a ton, let it cure overnight before you fly.

that said yeah check your props. a prop that took a hit can be slightly warped and you wont always see it visually. the vibration will absolutely work screws loose over time especially if youre doing anything aggressive. swap in a fresh set of props and see if the vibe drops on the blackbox logs if you have logging enabled.

had almost the exact same thing happen on my Source One build weirdly enough. turned out one of my motor screw holes had started to strip slightly so it wasnt actually getting full torque even when i was tightening it. ended up using a slightly longer screw with loctite and it sorted it. probably not your issue but worth checking if one particular motor keeps being the problem one.