I agree with Zaela that the Titanium client is missing the part about 6000-6079, probably removed when they changed the merchant window to use listbox.
also probably hardcoded in one of these files:
C:\Program Files\Sony\EverQuest>findstr /S /M /C:"EQType" *
eqgame.exe
eqmain.dll
here's a link to multiple eqgame.exe's. you could try finding one that recognizes 6000-6079
Edit: these are actually pre2002 so probably dont support the XML clients
https://web.archive.org/web/*/http:/...wnload/patch/*