I was caving & I randomly fall into a pit & started burning, I got into creative mode, then started breaking stone blocks and they started getting replaced with Lava blocks, all of these were with ray tracing turned on, I turned RT off & Lava magically re-appeared in put, it was a weird experience & a weird bug, I currently can't provide a way to re-produce it but I've been seeing people complaining about this bug lately, so I'm reporting it for now until I find a way that can Guarantee this bug happens.
Images:

Those few Lava blocks you see in the middle are where I destroyed the stone after I got in creative mode.

Now with ray tracing turned off:

Lava magically appeared in It's place.
I faced this in latest beta & I've seen other people reporting this issue to me.
resourcepack was (https://mcpedl.com/truly-vanilla-rtx) but I Highly doubt a PBR resource pack can cause this (there's even someone in comment section there pointing out this bug!)

My Current way of Re-producing it.
1. Create a world with a PBR pack & ray tracing + Caves & Cliffs toggle enabled
2. Start going around in caves & find some lava pools with ray tracing, you should be constantly switching in caves because there's a high chance you will miss Invisible Lava polls with ray tracing turned on.

I'm still not sure about the exact cause of this, It randomly happens in some situations.