I have had my share of odd earths causing odd things to happen. But recently the engine has not turned over too well, almost as if battery not in very good nick. Sometimes intermittent. Used Landy in dark this weekend (don't very often) and noticed dip headlight out on one side. Thought it was bulb but no. Cleaned earth wire and live in bullet connector and sorted it. Landy starts first time every time now..
Perhaps there is a shorted live wire somewhere and I have moved it??

While sorting out your headlamp you may well have moved a short in the loom or more likely improved a connection some where as you pulled things about. Worth putting a meter in the live lines and seeing if power is going some where when it should not be,can't be much or fuse would go or smoke escapes.[all electrics run on smoke and when the escapes it's f-----d]