but has always lost more than he though was correct during recrystallization...
Two possibilities:
1) A lot of your 'product' was not MDMA. You need to distill or otherwise clean up more before attempting a recrystallization.
2) You are doing it wrong i.e. using the wrong ratio of solvents or the wrong solvents. Check you have these correct, and do some reading on recrystallization techniques in a chem manual of some sort, then come back and UTFSE to apply it to MDMA.
Happy gassing! 8)