Sudden death upon loading

I found and was exploring a new bastion in the nether.  I saved the game and had supper.  Upon reloading the game an hour later I appeared trapped in black stone and suffocating, not only suffocating but in the latter stage of suffocating (half heart).  Despite having my fully enchanted netherite pickax on the hotbar I died before I could get free.

steps to duplicate??  I don't know and I really don't want to do it again anyway.

What I expected: To reload safely and continue my exploration.

What happed: 'You Died'