Odd starter symptoms solved: loose battery ground

I want to share a solution to a problem that had plagued me for years, in case someone goes internetting for it in the future. The symptoms were these:

Starter would sometimes work, and when it did, it worked relatively well. Whether it worked seemed random.
When it wouldn't, my bike dash would go black, then slowly build back up.
Pop starting the bike worked well enough, though sometimes (rarely) it would not spark until I'd run it over several turns. This was exhausting for my 4k mile rides.
Headlight seemed fine.
After warming up, the bike would pop start easily.
The battery read fully charged, and passed a load test both on my multimeter and one at a shop.
Bridging the battery sometimes turned the starter over, but was not definitive.
Bridging the solenoid did not seem to work, but was also inconclusive.
The solenoid usually clicked.

So, the solution was painfully easy. The wire coming off the negative terminal of the battery ran to a loose bolt on my engine. When I removed the bolt it sheared off. I reattached the ring connector under one of my clutch cover bolts. Starter worked first try, and the bike even seemed to spark more reliably.

Sometimes it really is a simple solution.

My beloved bike still knows how to make me feel like a dummy!