Yeap the locks are heated, could you hear the lock pump running in the boot when the remote was used, as it opened manually, which suggests the vacuum system isnt running at 1st, manually works by mechanics as such, wire pulling the latch, just an idea maybe the pump has frozen or the vacuum isnt enough to release the frozen latch where as a manual pull would.
The locks on my 8P & others with keys work by a plastic round piece in the lock mechanism, that hits a microswitch that signals to unlock/lock so, but iirc from my S3 the key used to only do that door & seemed mechanical not electrical, but could be different tbh as they changed parts very often, strange key didnt unlock unless yours is a facelift as I seem to remember they changed something on the locks.