IMPORTANT EDIT:
further inspection revealed that the Banners/Signs might be changing to Banners/Signs because the location is corrupted, as soon as i use a clone command that places another Banner/Sign to the location of the LAST Banner/Sign, after the first one got removed, it corrupts as seen in the screenshot.
this actualy might be the case, because my Tank can move back and forth via "/clone move" command, and the game doesnt like if two Banners/Signs ever existed in the same location.

you can clearly see at:
1. the hitbox of the "Banner" is formed as a Sign, as it previously was one.
2. the chat says something like: "couldnt not locate sign"
as soon as i use the SAME clone command several times.

more specific about the clone command:

• i use a /clone masked move command, to move a structure (Tank) relative to me two blocks ahead (north, south, west or east), keep in mind that
  the structure is inside the loaded chunks.
  if i use the clone command more then arround 4 times, the chat creates:
  "couldnt not locate sign" for every Sign OR Banner insides the cloned
  location, as seen in the screenshot.

>>> What I expected to happen was...:
the sings and banners should,ve been clone correctly to the set location

>>> What actually happened was...:
the signs and banners eyther swapped places or changed into a sign OR banner with the error messge in the chat

>>> Steps to Reproduce:
1. make shure you died once and spawned somewhere completely different than you actualy spawned first (it might be the reason)
in a "redstone ready" flat-world
2. be in the positive X and Z coordinates
3. crate a command inside a command block that is supposed to clone a location, relative to you, including Signs and banners 2 blocks further away.
!!! make shure that the command is executed every time you want to move the structure, that is nearby you, a few blocks further, so that the locations of the
front sign/banner and the back sign/banner WILL swap theyr places soon.
4. or just download the save file, go into one of the tanks and press the same wooden button over and over again.

OUTCOME:
as seen in the screenshot

FIX INGAME:
reloading the world helps