Solenoid / converter issue? Trouble with battery disconnect

Take a quick look at this page that explains the surges and why/how to use a diode for surge suppression- specifically for solenoids.

My Grandfather had a lawn tractor that kept eating solenoids, about once a year. After this fix, no more problems ;)

Solenoid surge suppression with diode

And, yes, a surged solenoid will act "sticky" as it seems like it engages, yet doesn't pass the starter enough current. I once thought it was a low voltage COM line or bad ground or hot contacts because of the way it acted ;)