Gi was wraparound with ties?
My tkd dobok top is crossover with a zip, my kickboxing top is v neck pullover type, but almost the same cut - both ride up on me. Tucking/folding the sides under where my belt runs seems to reduce it slightly, taking them in a bit at the waist might work...
Can't really say it's my feminine shape that's the cause - what with being 5'10", 150lbs, and male
Oddly, the... erm.... less svelte members seem to have less trouble than me...