I try to reproduce your problem, delete the standard.wad
apply brick texture, save, compile and run, same error as
you did pressing key 1, then I add back the standard.wad,
the "Sky_gorge" texture appeared again.

Probably the problem is your standard.wad, try to update
to 6.40.5 once again, before doing that, save the old
standard.wad to another place and delete it.