The input jack on my NG3 moves a bit when I wiggle my cable.
I can turn the threaded part which is visible from the outside with my fingers to the left and right.
Is this how it is supposed to be?
Signal is fine, no crackling or anything.
I am just curious and I don't want to screw out the input jack to have a look.
There is a nut visible on the outside of the instrument that holds the jack in place. It sounds like that nut is loose. You might be able to tighten it with a socket without taking anything apart. If it spins too much, bad things could happen. So to be safer, you might want to unscrew the screws and slide the whole assembly out a little bit, just enough to hold on to the jack so you can tighten the nut without the jack spinning.
With that. I’d take the cavity cover off while doing so to monitor things on the inside while doing so.
A small dab of red(?) thread locker wouldn’t hurt either. Not blue though. Can remember the colour code but the minimum strength one.