Maybe it is due to there not being enough video memory available. That error seems like there is a problem creating a texture.

When running through your levels individually, the video memory is probably enough, but running them together uses too much/

You could try to fix this by using functions such as 'ent_purge' to unload the video memory used by entity's / textures.

I haven't much experience with the level building side of A7, but I am aware of a few people having to make workarounds so the level can run properly.

You should wait for a more experienced person to answer,