That's a DOS/Windows problem.
WILDFILE uses the DOS command "DIR" to get your filenames and that command fails here :-(
Try it in a DOS box manually:
Assume the four files
DIR *.TXT lists all the four files.
But fascinating a
DIR *.TXT1 lists only the last two files.
DIR *.TX lists no files.
So it seems that DIR behaves wrong if the search pattern contains 3 letters.
Then it only checks the first three characters of the extension too (it seems to check the 8.3 short name only here).
Unfortunately VEDIT/Wildfile has no chance to get around this.
(At least I can't see one. Blame it on MS.)