TCAS TEST 737NG
 

Do you have any idea why a TCAS TEST may fail if the airplane is parked in a particular position on apron?
It Happened today. I was parked at a particular jetway and the TCAS test was failing. The maintenance crew told that as soon as they started the pushback procedure, I should do the test again and it would work fine. I asked him why was that, and he told me that nothing related to it was found in the manuals, but their experience...
It worked...
Any ideas?

TCAS Test
 

IRS's to NAV? Seems to be the reason on the Classic.