[Admins]

If you want to have both new and old tileset layouts on the same server, there are some server options you can use, since the server is not seeing what you add with addtiledef and so doing wrong onwall-check:

newtilesets=true

would use the new tileset layout in all levels,

newtilesetlevels=main_,level13.graal,insidehouse

will only use the new tileset layouts on levels that start with one of the listed strings (all levels starting with 'main_', level13.graal, all levels starting with 'insidehouse').
I hope this is helping a little bit, I was not sure if those options are already well known.