Coming home from fishing yesterday my port side brake made a loud bang/klunk sound and I could feel it almost lock that tire up, it actually did skid a tiny bit. It just happened about 1/4 mile from home, no issue the whole time until then. Finished the drive home slowly, every time I touched the brakes it would make the same noise and really slow that tire. I took both drums off and inspected the shoes and mechanisms. No visual issue. I installed new loaded backing plates last summer and flushed the fluid. Brakes worked perfectly until that one instance. Adjusted the brakes a little and put them back together but that one side still does it. Working on them again today instead of fishing like planned,. Any advice is much appreciated. I can usually fix anything right away but this is weird. Maybe I overlooked something yesterday.