How can I prevent stack overflow from a recursive function?

Hi, I have one big table named tbl, and keys titled as Blocks. Here's an example of how I have each Block set up:

tbl.Block4 = {
	{
		{
		Sensor = sensors.X3,
			Signal = {
				Model = signals.S3A,
				PathOptions = {
					{
						Name = "Station",
						Switches = {
							[switches.V2] = 2
						}
					},
					{
						Name = "Main Line",
						Switches = {
							[switches.V2] = 1
						}
					}
				}
			}
		}
	},
	{
		{
			Sensor = sensors.X4B,
			Signal = {
				Model = signals.S4B
			}
		},
		{
			Sensor = sensors.X4A,
			Signal = {
				Model = signals.S4A
			}
		}
	}
}

I know, the tables go super deep, but I have it that way for a reason. My goal is to give each table with the sensor and signal inside it another table called "Adjacent", which contains the other table that has the same sensor value. I have a recursive function that I got with the help of the community here:

module.tableRec = function(tbl, func, level) --Add an OPTIONAL paremeter to be used in the recursion loop.
    --If we weren't passed a recursion level, assume we are starting a recursion loop and set to 0
    if not level then level = 0 end
    --Add printouts for debugging. Also, use typeof - (it's more compatible with ROBLOX)
    if typeof(tbl) ~= "table" then warn("Passed table not a table!") return end
    for i, v in pairs(tbl) do
	    func(i, v, level)
	    if typeof(v) == "table" then --If we have found a table, call the recursive function on it!
	    module.tableRec(v, func, level + 1) --Add one to the current level to indicate a new level of recursion
	   end
    end
end

Finally, this is what I'm doing to get the adjacent points. It seems to work, until a stack overflow happens.

function findAdjacent(value)
    functions.tableRec(tbl, function(i, v, level)
	    local block
	    local endPoint
	    if level == 0 then
		    block = v
	    elseif level == 1 then
		    endPoint = v
	    elseif level == 2 then
		    if v ~= value and v.Sensor == value.Sensor then
			    print("found adjacent")
			    value.Adjacent = {block, endPoint, v}
		    end
	    end
    end)
end

functions.tableRec(tbl, function(index, value, level)
    if level == 2 then
	    findAdjacent(value)    
    end
end)

I would really appreciate how I could identify which tables share the sensors without putting too much stress on the game. Thanks!