Advanced Question on Disguise Self tricking racial gear

Didnt know how else to phrase this question besides calling it an Advanced question but as many know Disguise Self lets you pass racial requirements for gear. A lesser known mechanic is you can the drop the Disguise and continue benefiting from that gear.

My question is what exactly makes the gear check for your race again? My specific case is a drow Eldritch Knight wanting to use the Soulbreaker greatsword. I do the trick (and drop the Disguise) and it works for a while but it seems to randomly drop the extra psychic damage from being gith. It sometimes lasts multiple fights. Sometimes it stops mid turn after working for the first hit and then poofing away.

Sure, I can get it to work fine if I stay in Disguise but I like looking like myself (and I am not wanting to use mods) so I was curious if you guys know what could be the issue. Im also not unequipping it or crossing maps when the trick needs a reset since I already know those reset the race check