Ben - sorry this has happened to you.
On corresponding with the bands, how man times do you check in with them after booking a date to confirm?
While it may not solve all your cancellations, it may be helpful if you're being booked more than 2-3 weeks out to call them or meet with them as a reminder - can be to ensure they haven't added a second drummer, baliphone section, etc. but also reminds them about the gig in a good way vs. a nudge way. Remember, many, not all musicians are creative folks, but not necessarily the best with dates and numbers...
We do a similar thing when our band books a bar - we call 1 week prior to confirm the show, and then to get details on when we can load in, who will be there, etc. When I set the date in my iPhone, I add an alert 1 week prior to call and another 2 days prior to get all our gear together.
This may help you out on limiting cancellations, but also can build stronger rapports with the bands.