When you save a map in Lönn, normally it will check entities, triggers, etc to make sure you have dependencies listed for everything. It will not check the Wipe field in Map Metadata, so that particular dependency could easily be overlooked. If the mapper and testers have those dependencies enabled in game already (which is likely) then the map will run fine, but will otherwise crash when you spawn at the start.
#Dependency checker doesn't account for screen wipes
summer stump
lone frost
that's kinda unavoidable. lönn would have to read the code mod dlls to check which mods screen wipes are from, which doesn't really sound feasible
the existing dependency management stuff is
- entities and triggers, which mods have to provide plugins for, so lönn knows which mod they belong to
- files (textures in particular) where lönn just has to check which mod a file comes from