Both suggestion are ones to check out.
Switch (and motor connections).....loose/bad terminals
Also check the wire connection at battery
In-Line DC circuit Breaker do causes issues but you should replace with one that is properly rated for the motor and wiring otherwise might as well just hard wire.
Is it time for your medication or mine?
2007 DODGE 3500 QC SRW 5.9L CTD In-Bed 'quiet gen'
2007 HitchHiker II 32.5 UKTG 2000W Xantex Inverter
US NAVY------USS Decatur DDG31