Franklin Electric’s selection of SubDrive15, SubDrive20, SubDrive30, SubDrive50 controllers use state-of-the-art technology to provide constant water pressure through variable speed control of submersible water well pumpshttps://www.rcworst.com/franklin-electric-5870205313c-subdrive20-connect-submersible-motor-constant-...
variable speed control of submersible water well pumps
VFD (Variable Frequency Drive)
The controller should have had a noise filter built into the unit.
Here is an example of a VFD noise filter
https://www.amazon.com/Filter-Suppressor-Variable-Frequency-Drives/dp/B08BZ6BGN7
Only an example.....
I would suggest you contact Franklin Electric Tech Support and tell them the problem you are having.
Ask them what noise filter they would recommend. Also the best place to install the filter. I would assume near the SubDrive controller.