I'd noticed it seemed like sometimes spawners, especially those in ruins or pyramid basements, weren't spawning anything even during the proper time of day. This was confirmed when a friend tried to make a grind room; and no barbarians have spawned over a long period of time.

Thank you for the report!
You're indeed correct, that this is an issue - mostly in the pyramid basement.
Bandit spawners would still need enough daylight to function properly

ok awesome, thank you!