After a single 2 hour session noticed that all double chests in the Nether around my 2 main bases in OW (approx. 200 blocks apart) had been converted to single chests and all the single chests (that previously contained items) were completely empty. Deleted world and carried on with unaffected backup - annoying, but its Beta!

What tasks I has been doing leading up to bug+observations

1) Trying to fix NPortal that linked to 2 overworld portals depending on which orientation you entered the Portal+which L or R side you entered. Both OW portals were quite close, however, one had a very high Y value and I expect the Euclidian distance on the diagonal was affecting the X and Z placements (I always match my portals properly). Fixed in the end by moving 2 blocks on an axis. Entered to and from Nether on numerous occasions. Sidenote: Wish we could assign portals manually.

2) Got hit by a ghast (as you do) in my central hub; seemed like a weird explosion lifting me 5-6 blocks into the air. I noticed 2 blocks of a smooth stone wall had been destroyed in the explosion / netherbrick surrounding the stone wall was unaffected

3) Changed simulation distance from 12 to 6 chunks. Never done this before but wanted to test modified mob despawning rules...

3) Bred lots of rabbits, turtles for eggs, chopped lots of lumbar; normal MC day - nothing that should have caused this bug.

Note: Chests 150+ or so blocks away from the converted/wiped ones seem to be unaffected

Note: Searched for a similar issue but couldn't find one, so created this.

HTH