@Bluebellflora
That's the problem that I'm not understanding - it shouldn't even be possible... but I tried it again last night with three different tests: one with a repaired game, one with a brand new game folder, and one with a full uninstall/reinstall. For each test I put absolutely nothing in my game except the Peacemaker Caine Living TV (fresh download from Peacemaker, as the package file isn't in my mods folder anymore anyways since the start of this problem). No mods, cc, saves, or tray files. Loaded up the game, started a new save, loaded a lot, and placed the Caine TV, and the glitch showed up. For each of the three tests I tried this process twice - once by loading into live mode, then entering build/buy, and once by loading directly to build/buy from the map view.
I'm absolutely stumped.. because you're right - using the same steps we should be able to reproduce the issue and find common denominators. But so far, the only common denominators are that we're running The Sims 4 on Mac and that the problem starts by appearing on CC objects.. beyond that, it's a mystery to me.
By the way, I also posted on S4S forums last night with some details and a link back to the thread here. Didn't want to repeat everything in case I was posting the message in the wrong thread/board at first, or in case posting the same super long thread on two different forums is considered bad etiquette. Either way, no one has replied yet, but I'm hoping that because there are a good deal of CC-creators over there, someone may have a clue about what might be going on. Especially because LittleDica and Peacemaker themselves both seem to be pretty familiar with the mechanics of cube maps, according to the threads I've found over there (the one you linked as well as another where Peacemaker gave some advice to another creator about a cube map issue).
Anyways, I'm going to go in game and do more testing with the variables you mentioned in your second message. So far, I've gotten the glitch when quitting the game from build/buy as well as live mode. But I'm going to lay out a few more tests to try to isolate the different variables that could be affecting the issue, and I'll go from there and report back.
Also did some exploring in S4S last night, taking a look through the warehouse tab at the resources associated with the package files of Peacemaker's Caine TV and a base-game EA TV. Didn't find any differences that jumped out at me as clues, but I can keep looking at some of the other objects that have appeared with the glitch and maybe I'll find something worth noting.
Last, just wanted to make sure you know how grateful I am that you've been working so hard to help me with this problem. It's certainly not an easy one, and it means a lot that you're spending your time helping me figure this out. Your work is deeply deeply appreciated, seriously. Not just with this case, but with all the work you do on the forums here.