Cold AND wet is the big problem
If the are plumped up with water then freezing can really do a number.
Bridges I've found are the first to succumb and melt if not catered for.
Need constant cold for a true dormancy, a blue sky winters day is enough for heat for a few hours for most to try to punch a bit of growth if there is some soil moisture.
Under 8 degrees for a least a fortnight(day/night) is what I think brings it on. But if it gets above it you need a reset. No science to my thoughts, just watching.
Some of our European members might have better thoughts. I get well minus cold and some years a fair bit of snow, but it's not constant... Pretty sure I've only had dormancy a few times, mostly Damn slow growth otherwise.
I focus on keeping em dry these days and let them do whateva they want until it's time to water them regularly . If hard pressed even getting them hard up against a wall under the eaves will get most through.
Dont forget to use whateva microclimate you can.
Edit - smaller pots also seem to be more likely to succumb, than a larger one with a well draining mix.