Motorola Backflip :: Reboot Loop Discovery?

I purchased a used Backflip and almost immediately started having the re-boot issue, which I since have learned is very well documented. Next time I'll research the forums b4 buying!My Backflip would spontaneously re-boot and then get caught in a constant cycle by rebooting less than 1 minute after my home screen (finally) appears. It never seemed to be triggered by any specific action, such as pressing the infamous "J" key, or using the camera, as others have stated.Through my research I determined the first thing to do was a reset to factory settings. That took time, but didn't solve anything. Then I went down the loose battery/business card shim route. I have 3 BN80 batteries. None of them solved the problem, nor did any of the various business card shim configurations I tried. All of my BN80 batteries are rated 1380 mAh/5.1 Wh. One poster claims that there are 2 different versions of that battery and the correct one is rated 1320 mAh/4.2 Wh. So I tried my BN70 from my Moto Karma (1140 mAh/4.2 Wh).

I also have 2 SD cards and it re-booted with either of them, and with neither of them.So I mumbled something unrepeatable, and gave-up. :-( I pulled my sim card and stuck it back into my Q1 Karma.Then I thought...could it be? So I re-tried the Backflip and viola! No problems. It's solid as a rock. I can browse the web via wi-fi and use all of the features. I can open it, shut it, use the camera, push any key (hard), including those on the battery side of the keyboard (even with the thinner profile BN70 battery) and I can't get the thing to re-boot! That is until I insert a SIM card. The very same SIM card which works just fine in my other Moto phone.