I can not convert two ASINs to FBM for the last two months

This problem started at the end of March, randomly 2 ASINs went from FBM to FBA and we lost a whole weekend of sales. The normal, select > action > change to merchant fulfilled was not changing them as normal so we submitted upload files. They would come back with absolutely no errors and then we would wait 24 hours, 48 hours and no change.

Support eventually came back and said that there was an error on their side and the SKUs were locked to FBA so we had to delete them and create new SKUs which we did and this was fine on 1 of the 2 ASINs. The issue then arose that because these are customisable products and the system could registry 2 SKUs to one ASIN, customers were then getting errors when they would try to customise so they could not purchase. All of a sudden the ASIN that was fine has the same problem. They asked us to do a delete and reupload and we are back to square 1. We are now into month 2 of waiting for Amazon to find the error and they tried to ask us to create new SKUs again, after I asked them to confirm that we would not face the same issue as last time because this is a customisable product is seems they have just resorted to asking us to do uploads in a constant loop and we are getting nowhere.

2 months of no sales of one of our best products. Has anyone every had the same problem and found a work around?