It definitely got better later in the season. At the end of July, I couldn't find any seed at the point when I wanted to start saving it.

A couple of weeks later, I managed to get a couple of 'normal' fruit (from which the current batch of seedlings have been grown) but was still seeing seedless ones. By the start of September it was no longer an issue: https://igenlode.dreamwidth.org/362379.html