Magnificent Mastery Beast Capture Bug/Glitch

I encountered a Soul Eater red beast that was impossible to kill because of a ton of extra life mods and regen. After spamming attacks on it, I realized it was giving red beast capture completion at a considerable rate. I went from about 250 captures, to the 400 required in a few minutes.

The beast was:
Razorchewer, Craicic Presence
Hadal Dive, Churning Claws

It looked liked a Craicic Squid mob type. When it would spawn it's minion mobs, it seemed like those were what was counting toward the completion indefinitely. It's either that, or the life/regen was doing something.