glob not working during startup

I have this weird problem with "glob" command, which returns empty list
during application startup but works as expected afterwards.
The command is:
set paths [glob -nocomplain -types f -dir $homedir -- {*.materials}]
and homedir ist C:/Users/Public on Windows OS.
The command is so basic, I have no idea were to start debugging.
Any saving ideas?
Many thanks
Alexandru
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