I have a little black box tester like that and some of my RM2's will not make a solid connection unless the bottom centre pin is unscrewed a little. When i am in a good mood - i'll unscrew it a 1/2 turn to get a measurement and then return it to how it was.
It does not stop any of them working on my Reo. If i am not in a good mood and don't feel like farting about, then i just get my multimeter and measure the atty either at the base from that centre pin to the threads on the bottom - or between the two posts the coil fits in.
Specifically i am trying to make certain i do not have a short in my build (bad for springs and batteries!), so i measure it all again with the topcap on - in case a coil is touching it. Paranoia works for me.
T