[Hectic]

seems its something with the bbu,
when you say lubed it you mean you poured a bit of oil into the bbu (in the blue thing)?
with the slide of if you use yer finger to move the blue bit back n forth can you see the piston head thing inside is it sitting flat and mooving freely?
seems it is damaged or dryed out or sticking if it worked when lubbed then stopped after the lube was all blown out then the piston (its baisically just a rubber piston head) is prolly dryed out or damaged and the lube fills in the gaps for a short time.
lets see if anyone else has input im no gun doc per say but i work on my own guns and have seen theese symptoms befor but they wer an easy fix for me (tighten the screw)