Thank you, Lee F for the suggestions to try. All makes sense. 

           Freddie.

I recently acquired a Williams GG-1 #2360 circa 1983- green 5-striper. Orig Williams box but no manual. Engine wrapped in 1983 newspaper. Engine clean and paint/sriping good.
- both wheel sets geared but only one roller set. No evidence of second roller set having been installed. Only headlight on roller end of engine lights. Motor runs good.

Problems:
- front roller pops up frequently on switches and crossovers and gets stuck to the bottom of motor housing - magnetic? Then engine slows and stops after about 10 feet of travel - appears to short out. Roller spring tension seems Ok.
 
- end trucks barely sit on track and jump around on switches, etc then derail. Were these originally sprung? Any suggestions?