mobile

Hi, everyone, sorry to bother you, but I'm in a bit of a pinch.
My unrooted stock Nexus 5 was running smoothly with then latest OTA update 5.0.1 until I got No SIM card error. I eliminated SIM card as problem source, removed SIM, discharged it completely and after few days turned it on and it was working. But problem returned soon and same method didn't show result. So things I already did:
- check my card in other phone: works
- check other cards in my phone: doesn't work either
- left it off without SIM for a few days
- erase cache
- upgrade to OTA 5.1.0
- factory reset
- unplug battery from motherboard for some time
- flash stock 4.4.4 from developers google com
- put some tape on card to make contact better
in this order. My next move would be to check if SIM card case pins are broken. Warranty expired month ago so there's that. Do you have any advice to give me? Is there any part of the phone that could've stayed not wiped during 4.4.4 stock flash and that's the reason problem remained?