Despite you saying it was fixed, my vote's for the blend door. There's no permanent "fix" for it. It'll break again one day. I replaced mine several years ago and it's broke again. Luckily it's no longer a DD and sits in the garage all winter, so I put off replacing it.
The good news is that it's the easiest thing to check. Just pull the glove box out (no tools needed - unhook the dampener cable then push in the sides to get it past its stops and it'll flop down by its hinges). Find the gray arm partially hiding behind the metal instrument panel bracket on the left, and try to turn it. If you're able to turn it, the blend door actuator is broke. Sometimes the gray arm itself can break as well, but it's usually the black arm that you can't see that breaks. The fact that you're getting lukewarm air says to me that the gray arm may well be broke.
