Oskar,
I'm sure that your average moved, you just may not have noticed it.
29 gets into the calc. as 58, and I assume that you're beyond the magic 400 rounds.
Imagine if 32 / 64 were your highest score in the mix, you'd drop 6 points from it (64 - 58), and 6/400 is 0.015 - visible as a .01 or .02 change due to rounding. Even a 4 points change would not stay unseen (+/- .01).
Nobody can look into your average calculation unless you stored all your Legend scores. Alas, I've more than once witnessed that s.o. did overlook a change or correlated it to a wrong individual score.
OTOH, I've never discovered a wrong calculation by WGT, and I've been looking into quite a few of them.
Anyway, the average should not be the most important item of this game - have fun and hit it straight - a 29 says you have none of the meter problems like many others!