I smoked Marlboros for a long time. Unfortunately, I am now dead but the cowboy in me lives on!

The air conditioner wouldn’t be an issue unless it happens to have a built-in ozone air purifier and pointed directly at the model. Ozone will dissipate and react fairly quick, so it’s generally not an issue. (There is a huge difference between an ozone generator and an AC unit that might happen to generate a bit of ozone.)

The sunlight would have to be as direct as UV doesn’t reflect very well off of walls and such. (~75%-90% loss) If you model wasn’t directly in a sunbeam, it likely wasn’t the problem.

Thanks for tolerating my troubleshooting for a bit. It would just suck if you had something you wanted to display disintegrate again. While we can’t fix a factory problem, we can possibly eliminate other problems, is my thinking.

With plastics, it’s UV exposure, specific chemical fumes or gasses that cause fast degradation so its easy to troubleshoot. ( … unless it was an underlying plastic formula problem or the nature of the type of plastic.)

Ok, I misinterpreted “disintegrating” in your original post. It’s unusual for parts to just crumble, so I took that to mean that parts were just falling off the build. My mistake.

Yeah, it would likely be a factory defect in the plastic. (Too much plasticizer, too little or even an incompatible dye, maybe.) Lego would probably be receptive to sending you replacements in that case as they are probably fully aware of any bad batches of plastic they had by now.

Most home windows filter out a majority of UV light from sunlight but not enough to completely prevent plastics from degrading slightly faster. Even if it got just a couple of hours of direct, filtered sunlight per day, that may have caused an issue over 4 years. (I have had plastics sag and crumble because of this over a similar time span, actually.) Just something to be aware of.

(Ozone loves to munch on plastic as well. If you have an ozone generator next to your model, that would be an issue. Some home air purifiers generate ozone, btw.)

There are what? About a dozen different plastic types Lego uses? There might be a batch of plastic that was used that is slowly shrinking over time from off-gassing. (Typical bricks are ABS which don’t have that particular problem.)

There might be a defect that someone else is aware of, but you might need to replace the connectors or glue them. Heck, you just need to fix the friction fit so creative use of PTFE thread tape might work.

(Not a Lego expert, but I do my research into plastics and such for other reasons. I want to guess that it might be the POM (Delrin) that is causing the issue which is absolutely not approved for use in spacecraft.)

Edit: Clarification on the PTFE thread tape use. For those who are unfamiliar with it, it’s not sticky and does not have any glue on it. If anything, it’s going to be a bit more slippery than other plastics. If you had two bricks and put a layer of PTFE tape between them, it’s would be thin enough to act as a wedge between the bricks to fix a friction fit but you should still be able to pull the bricks apart easily. You would need to experiment though.

Don’t confuse me with facts.

AI can’t recognize a pattern it’s wasn’t trained on? Imagine that…

I can’t find a source personally but there seems to be a bit of internet controversy on the subject.

A clip from TikTok said it was a secret signal for having syphilis. We can discount that just because of the source.

It could be from Rome or Europe, for reasons ranging from cleanliness to small hot cups.

Eesh. The Internet is useless these days.

Apophenia is real.

It’s worse. They completely believe their religions and it’s their god that commands them to kill the sinners. It’s a rationalization feedback loop: They are just doing what they are told to be proper religious folk.