Linking Cathedral to Cata 1 clone.

[Darkquake]

Hi trying to add a warp to a custom maze level in 1.13c I get:
"Halt Location : , line #826
Expression : Unrecoverable internal error 6fdbc62d"
Looking around on the forum people suggested that this was a warp related error but that's all i got.

It's meant to warp from the back of cathedral in act1 "tile 20", "vis 2" to a clone of catacombs lv1.
My Level.txt cathedral level has a "Vis2 137"(The next available id) with a warp type of 15(cath to cata).
My Cata 5 has a "id 137", "Layer 100", "Vis0 33" with a warp type of 16(cata to cath) and other than that is an exact copy of cata 1
I have copy+pasted the cata line in LvlMaze and changed the "Level" value to correspond the the Level.txt "ID" value.

So a few questions:
Does a maze level, HAVE to have more than one exit/entrance?
I've seen it in level.txt so I imagine it's fine but can I jump more than 1 Layer at a time? This is literally a 100 layer jump although the cath to cata is a 21 layer jump to start with so I assume it's fine
Are there some Vis tiles that are preferred by the game? There are 9 different values of Vis 2 warp tiles inside DS1.
Do I need to make a custom warp every time or is it generally safe to re-use a warp if it's for the same purpose?