So a year or so ago, I decided to create a peaceful world. I was digging out a small hill to make my house, but some of the blocks weren't breaking. I just broke a block and it placed itself back. I know this is something that happens often in 1.15, but I was still on the Aquatic Update, and that didn't happen then. I had problems moving around because it was as if someone had placed a barrier block in front of me. However it was a singleplayer no-cheats world. After a while, I started taking a lot of damage every second or so. There weren't any monsters around me as it was impossible and I wasn't using any mods. Does anyone know what happened? Has this happened to you or anyone else before?
EDIT: Thank you all for explaining, my friends were all going like 'hErObRiNE iT's hErObRiNe' and they didn't help me at all.
My guess would be invisible blocks, due to some glitch, causing suffocation damage?
I don't really know though.
Blocks coming back sounds like lag.
I did once have an invisible block that I just couldn't break, not breaking and coming back, it just didn't break.
I think it was single player but I'm not sure, no idea what version it was.
I just remember that for some reason it was in the way of something and I really wanted to remove it, I think I eventually could, maybe by digging out the blocks around it and trying from all directions.
I think that most glitches can happen in just about any version though some (most?) are more common in certain versions.
It's lag, even if it's more common on server, it can actually happen on single player worlds if Minecraft is running on a subpar PC which has several other application running (the number of them required to cause the lag is dependant on PC's resources).
If the player's head ends up in blocks that the client consider broken but the server doesn't, there is suffocation damage.