V400 problem

I recently purchased a new Motorola V400 phone on eBay. When I inserted
my SIM card and turned the phone on, I received a message telling me to
"Insert SIM". After playing around with the phone some, I was able to get
my SIM card to read by making sure the battery was pressing tight against
the SIM card. I put some tape on the battery to make sure that the SIM
card was being pressed against the contacts when the case was closed.
This worked initially, but after a few minutes, the phone would shut off
and then pop up with the "Insert SIM" prompt. Do I have a phone with an
isolated defect, or have others experienced this problem as well?

Thanks.

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