We had a problem at one stage that sounds close to what you have, we had the screen connected at both ends, to remedy took off screen at spindle end now left with 3 +Earth, ( 4-core CY cable) connected spindle to VFD, at the VFD end the screen was stripped back and finished at star point in cabinet, VFD was fitted in same cabinet on the same power line in.
Been running for four years no problems.

Phill