Bob,
I had a similar problem with my Arc SX2P mill. The forum members were very helpful.
Here is the thread…. Seig SX2P mill cutting out – https://www.model-engineer.co.uk/forums/topic/seig-sx2p-mill-cutting-out/
This is a summary of what I did to fix the issue….it wasn’t cheap, but the mill has been fine for over a year now.
Parts replaced…
– Speed control potentiometer, supplied by AliExpress – no difference made
– Main control board, supplied by Axminster Tools – no difference made
– On/Off switch, supplied by Axminster tools – no difference made
– 500W brushless DC motor, supplied by Axminster tools – Fault now no longer apparent. Mill has been test run for about a total of 1hr over a few days without issue.
And here is another thread on a similar subject…. Sieg SX2PG Mill – https://www.model-engineer.co.uk/forums/topic/sieg-sx2pg-mill-2/
Ches