Add Value variable stops working? Please help. #triggered

Please help.

I am building an interaction where you're asked to build a piece of equipment based on a specified order using drag and drop mechanics. The interaction allows the user to build the equipment in any order they think is correct, but they must follow the order listed to get the correct feedback. There are six parts to the equipment that must be drag and dropped in the correct order.

I am using a variable called Q1_Checker that is assigned to the correct drag object in each screen. The checker updates only when the right object is being dropped. If the tracker is equal to 6, the user should be shown the 'correct' feedback.

During testing, this is all working fine until the user gets to the 5th and 6th pieces. Here the variable stops updating. Additionally the trigger that causes the user to advance screen (on drop of any piece into the target area) also stops working. I have compared these triggers to all previous screens where this functionality is present and nothing seems different. Can anyone please take a look and tell me what I am doing wrong? Cheers!