Since this is apparently a derelict starship these kids find, I actually kind of hope the Janeway ECH is super-glitchy and one of the challenges they need to overcome is actually getting the program back on track. "Derelict" usually means "old" and/or "forgotten". It stands to reason it's been a long time since the latest patches were uploaded into the system and the whole core may be malfunctioning in critical (and potentially amusing) ways.
Except we already know the show is set 5 years after "Endgame," so it can't be that old.
The word "derelict" simply means "abandoned, deserted" -- the etymology breaks down to "completely left behind." It refers to any vessel or vehicle that's been abandoned with no intention of reclaiming it, whether it's an ancient shipwreck or a broken-down car someone left by the side of the road yesterday.