My advice:
Any time you see 73% chance to hit, save the game.
Then attack. Record the result.
Reload your save, and attack again.
Repeat at least 20 times.
If clinical observation confirms your suspicion, then post a bug report.
This might be a flawed approach, depending on how the game generates its random numbers. If they actually do a random number generation at the time of the 'dice' roll, then fine. But many games use a pregenerated random string of numbers so reloading won't necessarily affect a 'dice' roll.
