i have quite a few when i first started. but these 4 tops them all:
– cut the wrong length, realized at the end of the cross that i am 3 cross strings too short..
– mounted the racket wrong – this is a dumb one, didnt’ look at the 12 o’clock marker, and mounted one hole off.
– over tighten the top cross string. the top cross are so short that very little pull is needed to get it into the correct tension, don’t try to press the weight down. i have cracked a racket that way
– 4/8 o’clock support for slim frames. when strining a slim (ie. weak frame) racket, make sure you use the 4/8 o’clock support. there are a lot of outward pressure on that part of the frame when you are tensioning the cross from the top down, some weak slim frames may not be able to take that stress.