I store a value in coll with a symbol. I then immediately retrieve that value and 'set' the object which created it. This is so that the object and the coll stay in sync when modified separately. I am using route as more than one value is stored in the coll but for simplicity I have only put one in the patch.
Though, even using deferlow, I still don't get expected behavior. Here's a patch, try adding deferlow between 't b' and 'symbol file':