Thanks for the input. You guys are right. It has to be the mobile pump out service. Adds up too, as I discovered the most recent crack after the 1st pump out of the season. Game 1, didn't need the pump service. No problems. Game 2, also no problems. Pump out service provided and then the leak was discovered during the 3rd game weekend.
Well crud. The problem I have, other than the crack(s), is that there isn't a convenient alternative dump option. The site I store my camper on doesn't allow dumping into portable totes. I'll figure something out though.
Thanks everyone!