Sounds like your whole brake system needs to be refreshed.
After sitting for 20 years accumulating rust and corrosion I doubt that cleaning them is not going to restore the springs to fully operational levels. The retainer pins are probably weaken and could break causing a catastrophic failure.
I imagine that your TV is close to it's max towing capacity and still has drum brakes, so you need all the trailer brakes you can get.
If it was my TT I would do a complete brake job with all new parts, from the backing plates out.