Has anyone else had this sort of problem with a taildragger at walking pace?
Yes, I have, twice:
While flying jumpers in a beaten up (yes, not entirely airworthy) C 185 years ago, I bounced a landing into a setting sun a little. The 'plane gently started to go off to the left as I slowed. I applied and held full right pedal, and some right brake. The 'plane went at a walking pace, very much not under my control, exactly where I wanted it to go. I stopped looking like a pro, but knowing I had just gone for a ride. Curious, as to how I had not had control I had the tail lifted while I examined the tailwheel - it had no steering whatever, warn out pawls.
I landed my taildragger a few years back on a large paved runway I know well, in a high crosswind. I had no problem controlling, though I have full rudder applied quite a lot. As I let down the tailwheel, it unlocked from the steering because the rudder was deflected fully. As the 'plane slowed below a speed where the rudder was effective, it gently ground looped - application of rudder and brake would not prevent it. No harm done, but I felt silly!
I have learned the importance of maintaining the tailwheel, and assuring it does not become unlocked unexpectedly.