I know this is a very old thread, but wanted to add to it, so the info would be here for others to find:
I too, had the same problem with my CAL Delta Transport, that when the Drawer was opened, the Drawer would immediately close back up.
I tried some suggestions, as some mentioned a possible bad Belt, ordered a Belt from ApprovedAudio, no fix, pulled the Faceplate off, cleaned all the contacts, no fix, then tried something that a person advised, that the Micro Switches for the Drawer commonly have Silver Contacts, that they could be oxidized, and try a lit of DeOxIt on them.
They were a bit hard to access, hidden behind the Drawer Face, but once I got to them with some disassembly, and sprayed some DeOxIt on them, that cured the problem pronto, and 2-1/2-3 years later this bought in 1997 Transport is still working flawlessly ever since.
Mark