My fighstick had the now famous washer issue, I was about to send it back to madcatz but with the shipping costs of having to send it back and the wait time to have it fixed I decided to just mod it. Although, with the parts taking a week or two I decided to break it open and try to fix it in the mean time.
First, my joystick started sticking from day one, it wouldn’t occur often or long enough to warrant any concern. That was a mistake. What was happening: the washer was slipping out of it’s recess (see graphic below) which caused the sticking, then after enough tiger uppercuts the washer ruined my pcb board.
If your stick is sticking, decide whether to send it back or open it now. Don’t wait for your stick to be damaged permanently.
Bellow the yellow arrows point to the damage and the red arrow points to the soldering job I did tonight.

The fix:
Open it up-


Remove those four screws on the joystick plate and remove the stick from the case. There’s some glue on the connector so get a razor blade and be careful not to break anything

Pop the clear plate off. Use a flathead screw driver from the bottom. Then remove the switches and pcb and hope for the best.

Below you’ll see the washer (silver).

I applied some superglue below the washer, in order to make it stick (pun not intended). I didn’t take the whole thing apart, I just lifter the washer applied a drop and rotated around to two other points. You may want to go all out but if applied correctly you should create a lasting bound without affecting anything else.
Note: be careful, make sure not to get the glue anywhere else, I’m sure you know why.
After about 5 minutes of drying you can put the thing back together and start playing. Unless you have some damage to your board, like me.
Good thing my soldering skills are still there after 15+ years.

The red is where the connection was broken and I had to solder the connection back. The yellow shows all the damage from the washer.
Good luck…breaking your warranty and fixing your controller.