I just had this happen on borderlands 3, my save files corrupted so I restarted as Fl4k with the spider ant and fade away for my main skills. The page for Lavender Crawly talks about a glitch with having the pod stage and dying will automatically check it off, I had this happen about an hour ago for my first fight against her.
I was lvl 5 or so, nowhere near enough to beat her without fade away abuse. When I fought her and had her split into the second phase (split into the two Varkids), they went into pods while I was down and I ran out of time. When I respawned, I got the dialogue for defeating them and couldn’t respawn them until I save-quit the game. I haven’t had this happen to my other VHS yet but I thought it worth sharing that I replicated the glitch by accident, it could be just Fl4k but I could also be wrong. If it happens again, I’ll write it down.