OK gonna disclaimer this by saying I'm recovering from surgery RN and haven't been able to do any kind of upper body exercise for a month, and wont be able to for another TWO months so this is driving me crazy not being able to just hop up on the bar and film myself..

I have a pullup bar on my doorframe (it has three 'handle' options, wide grip, narrow grip and the perpendicular bar I think its called neutral grip?.) I can't do a lot of pullups, maybe 5 or so (what I thought was) good form with neutral grip or narrow chinup, and maybe 3 good form wide.

YET whenever I've hopped on the pullup assist machine in the gym I can barely do one with more than 50% of my bodyweight taken off. I've put it even up to 40kg and still struggled (I weigh 60kg.)

Am I using the assist machine totally wrong? Or is it that my normal pullups have really bad form without me realising.. I'm sure for my first pullup my feet being on the ground probably help (I don't jump up but I'm sure there's some kind of momentum there,) but for the 3rd, 4th etc pullup I'm starting from hanging (not dead hanging relaxing my muscles, I keep them tensed, but definitely extending almost fully.) Is it because pullup assist is a lot wider and higher?

Has this happened to anyone else before?