I can't destroy the sign I put on the chest

[Joe.exe]

USERNAME:
Joe_Kurumi

APARTMENT COORDINATES (F3 TO VIEW):
1831 48 622

ISSUE:
A long time ago (I forgot how long, but it was really long, more than two years) I put some sign on the chests, now I want to change the layout of my storage room, but I found that I can't destroy the sign I put on the chest.
Please help me destroy them, thank you.
Be careful, all the chests have my items.

ADDITIONAL INFORMATION:

 

[Hirathex]

ACCEPTED​

For safety reasons I've left the signs on, but you should be able to remove them now​