This is a weird one because it involves two different tricopters. My ZMR250 Dragonfly and my RC Explorer tricopter. Both had a crash. More like a hard landing than a crash. But each required a bit of minor repair. The ZMR250 Tri just rolled while I was trying to land a little too fast and the RCExplorer pancaked in and had it's antivibration battery tray/camera mount flattened (I was rolling and wasn't far enough off the ground!)

Both are flying Naze 32 but one is a Rev 5 and the other a Rev 6. Both are loaded with TriFlight. and both have Turnigy 210MDH for the tail Servos

I got them back up in the air and hovering but they are each behaving like they need serious PID tuning. But each was flying PERFECTLY before. Now one is giving me a yaw wag and the other a roll wag. I was thinking that it might be the props since they are the same ones from before the crash. Could that be the issue? Would a hard landing kill a servo? It seems to operate smoothly enough on the ground.

What could be the possible source for this behavior?

Maybe I'm looking at this in the wrong way. Perhaps it would be better to consider each as a separate case and then tackle them one at a time. Still, I need a place to start looking

Try to replace your propellers first. Unbalanced propellers cause vibrations which lead to unstable flying.
You can tell if your servo is damaged if it sounds different than before or it jitters or there is any free play.

I started repair work on the ZMR250 tricopter last night. I took the servo out and connected it to a tester. While it worked ok, I noticed a tiny amount of hesitation when switching directions

Because I had a spare one on hand, I replaced the tail servo. I'll hover the unit and see if that was the culprit. If not then I'll move onto the props. I want to change one item at a time so that I can find the source for this issue.

Btw, how does one go about balancing a three blade prop?

You shouldn't balance damaged props, just replace them with new ones.

How to balance a 3 blade prop (6 min 3 sec)

Success!

On the ZMR250 Tricopter it was just the servo. The props were fine (never were touched by the hard landing). I just flew it around the back yard and it was behaving just as well as it did before. Since it's my favorite, I've flown that tricopter pretty hard. That servo was the original one I put on there so it's no mystery it finally died.

The repair on the RC Explorer was a different story. I looked over all the 8" props, saw some minimal scarring from the crash and decided to trash them all. I just spent about 15 minutes balancing them and then reinstalled. I also remounted the FC with some new foam tape (just to be sure). And the tricopter flew just as nice and smooth as it did pre-crash

SBT: thanks for the video about balancing three bladed props. I was wondering how that was accomplished and now I have a good idea how to do it myself. I even have some rare earth magnets to use for that shop built balancing jig.