Maybe there was something in the wind this weekend because I had a similar problem.
Experienced but rusty PPL, starting a tailwheel refresher. Reasonable flight, a couple of cases where "I have control" hadn't been responded to initially, but it was no problem.
Return back to the field for a landing with significant crosswind, touchdown and roll out were OK to start with but then rudder movement became digital and it seemed prudent to intervene. "I have control" said I but found I couldn't move the rudder from full right, then suddenly it went full left, etc, etc. This ended-up with a gentle runway departure (on the downwind side) when the tailwheel decided it was time to break-out and a gentle low speed pirouette ensued with no damage.
My first ground loop!
We spoke about the meaning of "I have control" and I'll be more cautious next time.
BTW, tickling the nose, wacking, etc doesn't work if you're tandem
- thinks - maybe a long poll with a boxing glove on the end - but with hands on throttle and stick it would need to be strapped to some other part of the anatomy.