I'm aware there are issues with similar titles, but could not find one that matched mine exactly.

Chunk is loaded (shows block outline) but invisible. I can approach the boundary and walk out onto the invisible blocks. This seems to occur most commonly in the Nether, and it's only been in the last couple of days.

I made the mistake of walking into the invisible chunk in the nether, thinking it would load as I went along, and I lost a full set of enchanted equipment when I fell into a hole I could not see and died in lava.