Problem/Bug Blocks cant be placed...

So everything was running fine, but since the other morning , some blocks couldn't be placed.
Most of the stairs, wall, slabs, lantern. When me or the other server owner place any of these blocks, they simply disappear, if done in survival mode, the block is taken from inventory. I tried removing the WorldGuard region, but the problem remained. I dont know what information might help anyone with answering this, so just demand and i will post them

 

yes it is very close to spawn

 

but spawn protection is set to 0

I tried moving a few hundred blocks away and the problem still persists.

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

part 1 : https://pastebin.com/n5bwVjfK
part 2 : https://pastebin.com/RK49CAmW
part 3 : https://pastebin.com/TYSVcA9H
part 4 : https://pastebin.com/R8G1ifu7
these are all the logs i found in my server files. They are in chronological order, starting from one day before the problem arose