I'm going to have to stop doing these anthologies because there is nothing more upsetting to me than publishing late.
Honestly George, I've been in a lot of anthologies for a lot of people over the years, and with the single exception of Bite-Sized Stories
none of them published on schedule. Sometimes it's a few weeks late, one time it was three years
. It's a reality of publishing at this scale and of relying on other people to do things when they say they're going to do them. You do set yourself tight deadlines, and I'd suggest all you really need to do is give yourself a bit more time to turn things around on a production level.
Still, you've done several of these collections now, and with a pure pro bono spirit. If it's time to move on, you can do so knowing you've put out some seriously decent products, and arranged a lot of exposure for a lot of authors!