Aloha Toybrota
To be honest , we all have done it from time to time. It happens.
I think Ur friend is pointing U in the right direction. U might just have one of the pivot points sticking or caught a shoe in the drum. U might start by backing up & tapping the brakes as U do , U could lucking ? ?
Cralw under Ur truck & check out the cable , the adjustment arm then look at the axle. The pivot point on a top of the diff , follow the cable down both sides to the backing plate & check the levers there too.
U're just looking to see if the cable is still pulled tight or a wheel cylinder is forcing the pistons out against the shoes.
Hopefully it's that simple. Best of luck to U.
😎🌴