Issues with paint weight feature

[serrrg]

Hi people,

Using Maya since 2011 but just recently got into rigging.
I need to rig a simple packagi

ng box and I’m using the Skin Paint Weight feature on Maya but every time that I paint a joint’s weight, if I go ahead and check the previous one back, it gets completely different and messed up. I’m painting each joint again and again with zero results

I tried to lock each joint that doesn’t need to be painted, as well as reducing the max influences. Nothing has worked out so far
Does anybody have any suggestion on why this is happening?

Thanks a lot in advance!