Basically when you break a block in WorlgGuard protected region, the block will dissapear as if you would break it but won't appear again as it should so there is just a ghost block. Might be ViaVersion issue as well.

No errors to provide tho, doesn't throw any.

Same issue happens when connecting to a server on any major version that isn't your own, so 1.19 down to 1.12.

Similar thing happens when connecting to a 1.12.2 server in 1.19, specifically cubecraft and probably others

Also having this issue.

For future reference, here's a packet log (private): https://discord.com/channels/@me/1006300586301468692/1006300623727251537

Could the priority possibly be changed from low to medium or maybe even high because this also happens when doing simple tasks such as mining sand and anything.

I also have this. And it's not world guard only.
I'm using multiconnect from 1.19 to connect to a 1.18.2 server made by me and my friends.
On the server there are mines where ores are regenerated in set intervals. When the ores are regenerated some blocks don't show up leaving an air ghost block. Bumping into them is so annoying.
Right now I switched to ViaFabric and it works fine, that's so much better.
The blocks were regenerated by a command block (/fill command) and now are regenerated by a plugin, so we have 2 new cases, not only wg.
If you have any ideas why and where (in code) is this bug happening please share them here.
I really like this mod and I would be happy to contribute, but it's hard to open up a complicated mod made by someone else where you don't know what does what and try to fix a bug that has no errors, so I have no idea how to fix this : (