These would appear not to have any type of thermal break between the inner and outer portions of sash. Cold outer section -thermal break +warm inner section =condensation. Oh, could be that inner section is cold & outer section is warmer.
These would appear to be a very inexpensive window, you will probably see a lot of other problems with these, so they should still be fairly easy to spot even if the weather conditions have been pretty moderate. Plus stains or other evidence of moisture intrusion should be present.