One example: I tried to convince a male tower captain that his overwhelming tendency to place only male ringers around the back was a
problem. During the conversation he argued that 10 years ago the (entirely different) women at that tower hadn't been ringing advanced methods at all, suggesting that this affected his decision-making when placing bands today.

After the second or third time I talked to him, he did occasionally place me around the back, but he kept all the other women around the front. (This touches on a related but slightly different problem: the dynamic in most towers rewards selfish, ambitious, confident people. Anyone who is shy or unconfident needs an advocate or they are going to lose out on opportunities. This hurts unconfident people of all genders, but it disproportionately affects women.)

Another example: Tower captains (or other members of the band) will occasionally “make” shy female ringers ring a heavy tenor, or call a
touch, without providing the progressive practice necessary to make a success of it. This embarrassing experience hurts the ringer's confidence and solidifies the general impression that women can't do these things.

And another: An older male ringer was known to be both sexist in band placement (I once asked him if I could ring farther round the back at a 12-bell tower, and he placed me on the 5, before placing less-experienced male ringers on the 10 and 12) and conversationally inappropriate (making remarks about the appearance of young female ringers). People seemed to enjoy sharing stories about his behaviour but continued to invite him into bands and offer him positions of power.

In my experience, gender bias is more of a problem in more elite ringing circles. While really advanced ringing is mind-bogglingly male-dominated, small local towers seem to be more likely to be run by women or by men who appreciate ability in whatever form it takes. For instance, when I visited a practice in Leicester run by an older man, I was surprised and delighted to be asked to call a touch of surprise major from the tenor, something I had never been asked to do at my regular towers.

I’ve had several female ringing masters and tower captains, which has been wonderful. All of them were habitually ridiculed by male ringers for lacking confidence, making mistakes and asking "silly" questions. In my experience, most male ringers will respect and trust female ringers who have already demonstrated themselves to be very competent and confident conductors and heavy-bell ringers, and who appear to process information in the conventional ringer's way (i.e., very mathematical and theoretical, with a natural aptitude for understanding things like coursing order). Anything else is subject to well-intentioned ridicule, which further undermines the female ringer's confidence.

I’ve ended up thinking that women-only practices are the best way for women to improve their skills and confidence, which is a discouraging conclusion to draw. I do think a lot of progress could be made if mixed-gender practices were run by people who have been taught to take a firm line on teasing, mansplaining, tenor-grabbing etc. and to ensure that conducting and heavy-bell ringing are taught early and often to all members of the band. I would also love to see a real crackdown on yelling, ridicule, finger-snapping
and temper tantrums when things go wrong, especially if there are learners or less experienced ringers present (as the "Social norms?" story pointed out). Everyone brings their own history to the ringing chamber and a less hostile and intimidating atmosphere would not be a bad thing.