Level Restrictions

I'm talking about, when you go solo in a level, the level becomes restricted so no one can join you (until the next depth).
I understand why this is implemented for lucrative levels. But sometimes levels I assumed wouldn't be restricted end up restricted, and vice versa. Would being in a PUG versus a friend group before you go solo make a difference as well?
Is there a comprehensive list/page/explanation as to which levels become restricted once you go solo?

I believe going solo restricts your current floor, but the restriction is lifted once you progress to the next floor (this includes Basil floors, so be careful going solo there). As for others going solo, I'm not sure how that affects the restriction status.

I'm pretty sure going solo on a subtown or terminal won't lock your party.

If you join a party and go solo before the party does anything (not sure exactly what, but killing stuff and picking up crowns and things probably) then it won't restrict. Otherwise, both the party you left and the party you make are restricted until the end of the floor.
Not sure if that's correct but that's the theory I've been working under.
Boss floors and treasure vaults are naturally restricted.

@Traevelliath- Thanks for the reply, but I was referring to the level restrictions after you go solo.
@Demonicsothe- Not necessarily, because I've gone solo in d13 before the jelly palace levels and the terminal became restricted.
In general, what I'm trying to say is that I've noticed inconsistencies as to whether the party gets restricted or not. I've gone solo in a PUG in d27 right before vana and the party was not restricted. So not sure if there are bugs with going solo and restrictions or what :S

Hm, well if it does have bugs then that would explain why I've never been able to figure out the logic to it. One thing that may matter is whether or not it's the party leader or someone else who goes solo, but I don't really have much evidence for that either way.
It becomes restricted whenever you hit "Lock Party" on the far left party options.
The only exception is the boss levels.