It would appear there's an oopsie in the matrix:

This wasn't an issue previously with 0.15.0. Could you have a look please?

In my example is John Smith Legacy, and it's made with optifine features, such as CIT, connected textures, etc. I'm running on Fabric, with some extra mods to make use of said features, like CITresewn.

I am getting conflicting test results. I thought that perhaps shaders toggling was to blame, but rather than that, it appears the bug occurs in load transitions. The first load, be it in multiplayer or singleplayer, shaders or without, it all looks fine, no bug at all. If I swap however, be it by toggling shaders or by reloading the world or resource packs (F3+T), there's a chance the bug occurs. I can't figure out a reliable pattern, but it's the closest reproduction method so far.

One more thing I noticed is that this can also happen while I simply have the game minimized. It could be fine, I minimize the game, then after 5 minutes boom, textures gone. I've no clue why that is.

At the very least, I can't seem to make the bug take place with the default textures. I'm guessing it has something to do with JSL's 3D rendition of rail blocks?

I don't know. If you have any suggestions on what else to try, poke me.

Yup ill check

I'm not having the same issue in my testing world. Are they vanilla rails, and does this still happen when using vanilla textures?

Can you give me the resource pack you are using?

Since I can't directly link to the official page's download (and it's a bit buried there so you might miss it), I uploaded it to my mediafire: https://www.mediafire.com/file/43nb76xfstvo1l5/John+Smith+Legacy+1.19.2+v4.zip/file

Otherwise, visit their homepage and scroll down to the "Resource Pack History" bit, then a bit below you'll see a huge pile of yellow links, it's a scroll box, scroll inside of it to locate the 1.19.2 v4.

Have you had any luck in finding out what might be wrong? No rush of course, just checking in :D

Sorry don't have the time at the moment. I'm too busy with work

I have the same issue with ladders but on 1.19.3 and with Lithos resourcepack.

I can confirm this bug.