People who can't or won't firmly set aside one night a week for band priorities are everywhere, and this is one of the biggest red flags for flakiness there is. Personally I don't let very much get in the way of rehearsal night and I want to know that the people I am playing with are also committed to a similar degree.
It's one thing to let a very special event play through, but I have been in bands with guys who would cancel to take their wives out on our rehearsal night because the band they've been following and seen six times already that year is again playing in town. That happened more than once.
And then the following week it was something else that could have happened on another night, but got scheduled on rehearsal night. Etc., etc. If music is at all a priority, you schedule things on other nights, not rehearsal night, unless it just can't be helped. Kids' weddings, bar mitzvahs, ya know.. those things you probably need to do. Most other things can wait.
So, I would be sort of expecting this to not go well at this point. They say they have jobs coming up, and they are not rehearsing for those, obviously. Are they really that good? You struck gold, if they are. Odds of striking that kind of gold are low, IME.
I would show up with a very non-committal attitude just to see how things go. If it's a trainwreck where you know the material better than they do, you're out one evening. If it's a goldmine of seasoned musicians who can get things together quickly, you may have found something special. But I would expect personal scheduling issues to continue to plague this bunch because that is an issue that, IME, never gets better.