The black fabric on mine was peaking through also,
Here's an easy mod... Gather a liitle more of the black fabric, stuff the fabric into the wrist hole peg, re-insert the peg. The fabric would not protrude more than the TT forearm.
The fabric was too far down on my left arm as well. This caused the shoulder to look weird. MOST of these figures have this problem.
Don't cut off the excess. Don't stuff it into the wrist hole.
You need to work that black fabric sleeve back up the arm where it's supposed to be, so that the shoulder looks right. It takes a lot of patient lifting and pulling (otherwise known as "futzing") but it can be done. And if my experience is typical, once you get it up where it belongs it stays put.