Quoted from loneranger:I've had a few WPC's behave like this and I replaced the bridge rectifier (BR2 I believe) and all was well. The original bridge rectifier tested fine but must have been getting stressed under load.
Do NOT shotgun repairs.
Op...go to pinwiki.com and click on the WPC link. Scroll to 6.17 (reset section) and follow that guide. It will help you find the reason the reset is happening.