it's a known dumpster-tfs bugHave you tested it with Cipsofts client?
Do you have any source edits on your server?
I check,and test this in TFS 0.4 r3884 and Working Perfect. I had to solve something simple with luascript.cpp, i put the solution in the last.I just tested it and it works.
Feature - Perfect Autostacking Items 100,0% Stack All for 0.4 and 0.3.6pl1