Why is my Region3 being inconsistent?

I am working on a building system for my game, and I check if you are building on your plot by creating a temporary part where you are attempting to build, and if it is in the Region3 of that plot, then it places the object. My problem is that after some blocks have been placed, some regions of the Region3 go unchecked, returning that the temporary part is not in the region.

Video Example

Code:

game.ReplicatedStorage.Buildables.reqBuild.OnServerEvent:Connect(function(player, pos, item, color, material, color2, material2, hazard)

	local function build()
		local piece = game.ReplicatedStorage.Buildables:WaitForChild(item)
		local part = piece:Clone()
		part:SetPrimaryPartCFrame(pos)
		for _, object in pairs(part:GetChildren()) do
			-- Decorates object
		end
		part.Parent = game.Workspace.Placed_Blocks
		game.ReplicatedStorage.Buildables.reqBuild:FireClient(player)
	end
	
	local tempPart = Instance.new("Part")
	tempPart.Size = Vector3.new(1, 1, 1)
	tempPart.CanCollide = false
	tempPart.Transparency = 1
	tempPart.Position = pos.p -- Requested position from CFrame to Vector3
	tempPart.Parent = workspace.Ignore_Blocks
	tempPart.Name = "tempPart_" .. player.Name
	tempPart.Anchored = true
	workspace.Ignore_Blocks:WaitForChild("tempPart_" .. player.Name)
	for _, object in pairs(workspace.Stuff.Build_Plates:GetChildren()) do
		if object.Owner.Value == player.Name then
			--The buildplate has 2 Vector3 values for the corners of the area.
			--Corner1 contains the lowest values, Corner2 contains the higher
			local region = Region3.new(object.Corner1.Value, object.Corner2.Value)
			for _, object in pairs(workspace:FindPartsInRegion3(region)) do
				print(object.Name)
				if object == tempPart then
					tempPart:Destroy()
					tempPart = nil
					build()
				end
			end
			region = nil
			if tempPart then
				tempPart:Destroy()
				tempPart = nil
				game.ReplicatedStorage.Buildables.reqBuild:FireClient(player)
			end
		end
	end
	
end)

I was able to get it to work by without the region or the temp part. This is also a lot more efficient.

New code:

game.ReplicatedStorage.Buildables.reqBuild.OnServerEvent:Connect(function(player, pos, item, color, material, color2, material2, hazard)

    local function build()
        local piece = game.ReplicatedStorage.Buildables:WaitForChild(item)
        local part = piece:Clone()
        part:SetPrimaryPartCFrame(pos)
        for _, object in pairs(part:GetChildren()) do
            -- Decorates object
        end
        part.Parent = game.Workspace.Placed_Blocks
        game.ReplicatedStorage.Buildables.reqBuild:FireClient(player)
    end

    local p3 = pos.p
	local accept = false
	for _, object in pairs(workspace.Stuff.Build_Plates:GetChildren()) do
		if object.Owner.Value == player.Name then
			local c1 = object.Corner1.Value
			local c2 = object.Corner2.Value
			if p3.x >= c1.x and p3.x <= c2.x and p3.y >= c1.y and p3.y <= c2.y and p3.z >= c1.z and p3.z <= c2.z then
				accept = true
				build()
			end
		end
	end
	if accept == false then
		game.ReplicatedStorage.Buildables.reqBuild:FireClient(player)
	end

end)

Sorry to anyone in the future who was having the same problem and absolutely needs the Region3.