Corner of Peltier module is very hot
I suspect bad thermal coupling to the heat-sink.

Having worked on a few of these the tolerances and construction looks cheap. If the thermal coupling is not good they will get hot very quickly. Your numbers would also back that up.

I'd suspect one or the other, or both, is not flat. Also any small contaminant under the thing and it will not sit flat. They are also notoriously hard to hold down without cracking the ceramic.

Also... you mentioned condensation. DO NOT allow any moisture to enter the array. These things need to be heretically sealed to have any kind of life. They are also really easy to kill by over-driving them or through rapid temperature cycling.

There is a decent primer to read here.