making the right edge tiles walkable fixes it is SOME cases. not all.
it's a bit more involved than just an edge wrap in it's entirety and its really a sum of a lot of things. On one hand, it's related to collision, on the other hand it's related to wrapping of attribute tables,
and thirdly it's related to the actual reason why the nametables wrap as they do, which is camera movement. Thats why the posted fix seemed to fix it for the noscroll module, because the noscroll module doesnt deal with the camera
the same way scrolling modules do. (a simple extra check in those cases allowed the problem to more or less 100% vanish.)
This bug got a little better in my own project since the camerahandler is rewritten and it now correcly centers itself, preventing the edge wraps in some cases, but even so, it is still there,
and its the main reason why my project will eventually get the collision engine completely rewritten. This one can be band-aided with lots of band-aids but at the end of the day, might as well get it solved for good.
as far as coming up with a quick solution, no idea really, I'm more or less ignoring it for the time being until we get to properly dig into the root cause and see what has to be done in order to solve it the proper way.
there is a way to manipulate the occurrence of it to an extend by messing with the player speed, acceleration, and the scroll padding values though, which also further confirms the root cause.
if you set your player speed / scroll pad ratios in such a manner that the camera always moves a set amount of pixels and will never "go over" the edge (depends on movement speed and acceleration values) then the table will not wrap
and you wont have an invisible wall.
as for why the walls appear regardless of if the right edge is solid or not, it's because when you start scrolling left, the scroll buffers up half a screen worth of level data outside of the camera, and the moment it needs to pull more, unless you are dead-centered with your camera, it will pull the overflow column from the right edge (half a screen outside of the camera to the right if my memory serves me) and whatever happens to be there at that particular moment, will appear to the left nametable.