Just noticed that 2 chunks got unloaded in front of me when I am looking at them accross a diagonal of a third chunk, look at screenshot.

Found a way to reproduce the bug, will update in the next 30 min.

To reproduce the bug clear ou a full  chunk with height 2, then wall off one end of the chunk (as shown in Scr2.png). Then stand in the position that you can see in Scr3.png and Scr4.png.

Note that breaking even one block from the wall will load the chunk, as shown in Scr5.png.

Scr6.png Illustrates the bug again but in  a different chunk (adjacent to the previous one).

Note that if you have a further one chunk cleared up, unloading more than a single chunk is possible, as shoowin in Scr1.png and Scr7.png. This is because the edge of the screen now touches the end of the unloaded chunk, somehow forcing the chunk in fornand sometimes a few more to unload.

I have been unable to reproduce the bug in a new world in creative mode. Depth my have some role, in the screenshots I am at Y:64.

Another thing to note is that torches or sometimes even blocks do not prevent the chunk from unloading, as shown in Scr8.png

IMPORTANT: This also affect third person AND selfie camera views.