Update:
The variants are still avaliable, but not on first click after opening the UI.
Click on the multiple units main category, click elsewhere, click again and it works.

I don't seem to be able to replicate this particular issue, but I'd say its something to do with the game or the patch rather than specific to this mod. I'll keep looking into it though.If there's any extra information you can provide it'd assist me a great deal. Thanks!

btw the "0-6-0 Tender Engine (Cabless)" got no boundingInfo, see
https://www.transportfever.net/filebase/index.php?entry/5224-advanced-camera-views/#comment38371
(german, comments to a mod)

This likely has nothing to do with that issue, but who knows?

Ahh, okay, so that BoundingInfo issue is a compatability issue with another mod.

Unfortunately I can't release a quick fix for that as my local version has a few extra models I'm planning on adding to an update. I'll fix the boundinginfo for the 0-6-0 for my next update, but it won't be updated until the new models are ready.

As for the UI issue, I can't imagine they're related, but since I don't use that mod I can't be sure either way. Maybe open up a new game without the camera views mod and see if it still has that UI issue? That's the only thing I can suggest right now.

That issue was already existing two days ago before I added that mod. But the lack of boundingInfo alone could™ perhaps™ trigger that? Just curious...