[EscherechiaColi]

First error message:

user:/AddOns/RemiCustomAddon/RemiCustomAddon.lua:12: attempt to index a nil value /* <== this line is: RemiCustomAddonIndicator:ClearAnchors() */
stack traceback:
user:/AddOns/RemiCustomAddon/RemiCustomAddon.lua:12: in function 'RemiCustomAddon:RestorePositionBagSpace'
user:/AddOns/RemiCustomAddon/RemiCustomAddon.lua:34: in function 'RemiCustomAddon:Initialize'
user:/AddOns/RemiCustomAddon/RemiCustomAddon.lua:77: in function 'RemiCustomAddon.OnAddOnLoaded'

Second error message is basically the same but line uh... 43 if I recall correctly (this line)

        RemiCustomAddonIndicator:SetHidden(false)

Here is the "Bag" portion of the .lua file:

function RemiCustomAddon:RestorePositionBagSpace()
    local leftBagSpace = self.savedVariables.leftBagSpace
    local topBagSpace = self.savedVariables.topBagSpace
   
    RemiCustomAddonIndicator:ClearAnchors()
    RemiCustomAddonIndicator:SetAnchor(TOPLEFT, GuiRoot, TOPLEFT, leftBagSpace, topBagSpace)
end
[...]
function RemiCustomAddon:Initialize()
    self.inCombat = IsUnitInCombat("player");
    
 
    EVENT_MANAGER:RegisterForEvent(self.name, EVENT_PLAYER_COMBAT_STATE, self.OnPlayerCombatState)
    EVENT_MANAGER:RegisterForEvent(self.name, EVENT_GROUPING_TOOLS_READY_CHECK_UPDATED, self.OnLFGReadyCheckState)
    EVENT_MANAGER:RegisterForEvent(self.name, EVENT_PLAYER_ACTIVATED, self.DoesBagHaveSpace)
 
    self.savedVariables = ZO_SavedVars:New("RemiCustomAddonSavedVariables", 1, nil, {})
    self:RestorePositionBagSpace()
    self:RestorePositionFight()
end
[...]
function RemiCustomAddon.DoesBagHaveSpace(eventCode, initial)
    itemSpace = GetNumBagFreeSlots(1)
    if itemSpace < 10 then
        RemiCustomAddonIndicator:SetHidden(false)
   end
end
[...]
function RemiCustomAddon.OnIndicatorMoveStopBagSpace()
    RemiCustomAddon.savedVariables.leftBagSpace = RemiCustomAddonIndicator:GetLeft()
    RemiCustomAddon.savedVariables.topBagSpace = RemiCustomAddonIndicator:GetTop()
end

And finally, here is the addon tbug test that you required:
"tbug: No inspector for 'RemiCustomAddonIndicator' ("nil")

Once again, thank you for your time, and sorry for my replies hours, I currently live in Korea