"No SIM" after reassembly (water damage -> alcohol soak, new battery)

My iPhone 5s fell in the pool. Tried to dry it out by letting it sit for 72 hours in rice, but the phone was still stuck in a boot loop.

So I ordered a new ifixit battery, disassembled, soaked the logic board in isopropyl alcohol, dried it, installed new battery and reassembled the phone. And it works (almost) perfectly, except it does not recognize the (good) SIM card (as tested in another phone).

I've tried resetting network settings. The phone still has an IMEI displayed, so I don't think it's fried. Is the SIM socket particularly prone to hiding droplets of water/alcohol? Can the socket itself be replaced without de-soldering?

Any advice appreciated!