Good questions. The adapter would certainly be a point of concern for me. See if you can find someone (perhaps a nearby store that carries the controller) with an original adapter and test it. Although usually adapter problems are usually of the humming kind, static noises are not impossible.
1/4 to RCA is a potential problem as there is a relatively big gap in signal strength between them, balanced (Jack/XLR) being a lot stronger than unbalanced RCA. So keeping the master way down when going from balanced to rca is recommended.
Since recording internal really has nothing to do with the controller, I am not surprised the crackle/static is not there on a recording. Everything stays within the same (laptop) environment.
Btw, styrofoam is original packaging material, but there is a reason the equipment is always shipped in a (usually anti-static) bag. Styrofoam can be a major cause of static electricity. I would never recommended using original packaging for transporting sensitive electronics. Better is to get a bag (non-static inside) or a flightcase.
Other than that (trying a different adapter) I’d give the boys/girls from the Vestax helpdesk a buzz.
.
