I've had none other than the ones I induced with my own actions (e.g. gas shutdown drills) and since getting the beta firmware, have had NONE at all.
"FAIL" means the code reset, or the transmitter isn't (transmitting, that is.)
It can only happen a few ways:
1. The transmitter is physically broken.
2. The transmitter is out of battery power. Since you get warning a LONG time prior to it actually failing (the low batt warning is displayed on the computer while the transmitter is in use), this is 100% your fault; you ignored the warning.
3. The transmitter is MOMENTARILY obscured by something that blocks the signal. This is not fatal, but if it happens often you need to re-do where things are on your kit so it doesn't happen. The "free air" range of the transmitter is many FEET (like 6+); if your mounting doesn't permit a clear signal its probably easily fixed. (I have mine on my right post pointing down; it is EXTREMELY well protected this way by the first stage and tank, and is essentially impossible to "prang", yet it has a clear signal path to my right arm, where my computer is.) If this DOES happen the "FAIL" will go away as soon as the signal is reacquired.
4. The code reset because you allowed the pressure to go below 160psi. The only way this is likely to happen is on doubles during a valve drill. The new firmware addresses this problem, in that the code does not reset during a single depressurization event any longer.
If you're getting "FAIL"s, I'd love to understand HOW you're provoking them, because they're darn hard to provoke on the Suunto.