I also recall that bomb heading was realative, don't remember how i know.
Anyway bomb heading is ok, the strange thing is the vertical angle that sometimes is fine and sometimes you see the bomb overfly the target and then point down at 90 degreees...
In my first post i forgot to specify that i find JDAM inaccurate only in TOO mode, if I input coordinatest (UTM) into CAS page they are a sniper round.
My guess is that aiming with TGP is subject to error, but i can't be sure because i always try to aim to the ground where the target is but the result can change..