Only way I see, to place controller and SPS in fully closed metal box and use common choke filter:The 12V power supply is a simple 2A capacity wall wart, but it seems that its filtering is not enough for what I needed. When I switched on the motor controlling the wire tension, and applied a 14KHz PWM to it, spurious resets manifested every once in a while.
https://eu.mouser.com/ProductDetail/EPCOS-TDK/B82732R2102B030?qs=x3Z3TaiycdstnTWZCCNihg==