Question about Gemini Mini USA machines

Just how “fiddly” are the Gemini Mini USA claw machines? (The ones with the white housing over the claw piston, and have plastic claws.) I tried fishing for plush at one of them, and aside from an initial successful grab when I arrived at Round 1 today, all the rest of my attempts at the same machine have been duds, with the plush often slipping out as the claw unit retracted all the way back up. Even after I had an associate rearrange the plush so the ones I wanted were in the center, and reset the machine, it still didn’t grab securely. So what gives?