Shows go on with hiccups sometimes. Tech malfunctions or other unforeseen issues can occur. It happens everywhere that live entertainment is a thing. There's no such thing as a piece of entertainment where nothing goes wrong ever. If it's a regular thing, THEN it makes more sense to complain about it.
I get that B mode is suboptimal, but clearly they felt most people would rather see the show than wait much longer for it to come back with everything perfect, and in the grand scheme of things, that's probably the correct decision from the perspective of most parkgoers. If there's a huge failure or safety issue, of course, suspend performances. If *one thing* doesn't work and it's not a safety issue, they're gonna still run it.
There were certainly Fantasmic performances in the early nineties where not everything worked, people just didn't notice because there weren't 30 cell phones livestreaming every performance or huge internet communities tracking every single blemish or imperfection in the parks.
