50-70% of the models stopped working while in the editor.
The "Try rebaking popcorn assets" warning that you are seeing is normal/expected for the HD mode. Blizzard released a patch that broke these, and it is happening to everyone who uses HD mode in the editor and not just you. The patch also affected something about the DDS parser.
So, all of these problems that you are having are not because anything is wrong with your computer, most likely. These are happening because ever since August 17th, 2022, Blizzard released a patch called Patch 1.33 (and more recently 1.34) that were written by the 2020 Reforged team before those guys were let go, allegedly. But even though the people who made the patch were let go, and so it will never be finished, the new guy at the office at Blizzard wanted to get the "i did it!" credit for adding a ranked ladder to the multiplayer, so he released this unfinished patch without testing these kinds of World Editor bugs.
People have reported these World Editor bugs in many places and on the forums repeatedly. The new patch is reported to also cause campaign crashes for some players, in particular in the Rexxar campaign. Someone in the know has reported on the forums that for any user experiencing the campaign crashes, then that user should set spell effects detail to low and never load from a mid-map game save.
However, despite all of these known issues, Blizzard cannot fix them because the new person who is rubber-stamping the patch and releasing them and ignoring bug reports on Public Test Realms and stuff is a new person who did not even break this stuff. They just basically grabbed the "unfinished next game version" from some backup in the office at Blizzard. So these bugs that you are having are the new Reforged, and will not be fixed, at least until next year (but possibly not ever). Another known bug is that "Advanced > Gameplay Constants" option in the World Editor will crash the entire World Editor if you try to edit the Damage/Armor tables.
I read a post on the forums or Discord somewhere by an account that I believe (allegedly) is associated with one of the former Reforged employees who was let go in 2020 who still plays the game, and for those people who still enjoy the game and play it (not current Blizzard employee(s)) this guy said that when he makes his map(s) on Reforged now, he uses a backup of Reforged Patch 1.32.10 for the World Editor then plays the map(s) that he creates in that World Editor on the new Patch 1.34 live client. That way, he can have a stable world editor that will work better.
If you want to try to do that, obviously you will have two obstacles to overcome:
- Downloading the 1.32.10 world editor requires finding a copy of it online, as Blizzard Entertainment does not officially supporting downloading old versions. Or, if you're like me and already knew the new patch would break the game before it released because of the Public Test Realm and how they do not fix bugs on there, then you could copy your 1.32.10 installation before updating Warcraft III: Reforged on the computer.
- Even if you had last year's Reforged World Editor that has less bugs, any map that you save with the World Editor you have now will automatically convert to the new format and cannot convert back unless you use a 3rd party tool to convert the map back to the old format. If you find yourself stuck on this problem, it looks like the Map Adapter tool here might be capable of converting a Patch 1.33 or Patch 1.34 map into the Patch 1.32.10 format, but I have never personally used this tool so you may need to investigate further to see if it really works for your use case.