Weird issue with list variables

[Computerize]

I made the following skript:

command /whitelistblock [<text>]:
  aliases: wlb
  permission: blockedup.whitelistblock
  permission message: &cInsufficient permissions.
  trigger:
    if arg-1 isn't set:
      send "&f/wlb add"
      send "&f/wlb remove"
      send "&f/wlb list"
    else if arg-1 is "add":
      if target block isn't set:
        send "&cYou must be looking at a block to execute this command."
      else if {whitelistedBlocks::*} contains target block:
        send "&aThis block has already been whitelisted."
      else:
        send "&a%target block% &ahas been added to the whitelisted blocks."
        add target block to {whitelistedBlocks::*}
    else if arg-1 is "remove":
      if target block isn't set:
        send "&cYou must be looking at a block to execute this command."
      else if {whitelistedBlocks::*} does not contain target block:
        send "&cThis has already been removed from the whitelist."
      else:
        send "&c%target block% has been removed from the whitelist."
        remove target block from {whitelistedBlocks::*}
    else if arg-1 is "list":
      loop {whitelistedBlocks::*}:
        send "%loop-value%"

command /build:
  aliases: togglebuild, tb, buildmode, bm, b
  permission: blockedup.build
  permission message: &cInsufficient permissions.
  trigger:
    if {toggleBuild.%player%} is true:
      set {toggleBuild.%player%} to false
      send "&cBuild Mode has been disabled."
    else:
      set {toggleBuild.%player%} to true
      send "&aBuild Mode has been enabled."

on break:
  if {toggleBuild.%player%} is not true:
    if player is in the region "mainzone":
      loop {whitelistedBlocks::*}:
        if {_whitelistedBlock} isn't true:
          if "%event-block%" == "%loop-value%":
            set {_whitelistedBlock} to true
      if {_whitelistedBlock} isn't true:
        send "&cYou cannot break this block in the Main Zone."
        cancel event
on place:
  if {toggleBuild.%player%} is not true:
    if player is in the region "mainzone":
      loop {whitelistedBlocks::*}:
        if {_whitelistedBlock} isn't true:
          if "%event-block%" == "%loop-value%":
            set {_whitelistedBlock} to true
      if {_whitelistedBlock} isn't true:
        send "&cYou cannot place this block in the Main Zone."
        cancel event
      else:
        wait 5 minutes
        set event-block to air

If I did /wlb add and looked at any block it will say the block has been added to the whitelisted blocks and /wlb list shows the block on the list. If I place the block I just whitelisted then break it for some reason it adds air to the list even if it is already on the list and the block I whitelisted is removed from the list. I can't think of any reason why this might happen but I'd appreciate a fix