Amazon changing products categories / browse nodes

I have recently seen some big drops in sales for some lines, on looking at the listings I noticed many have had their categories changed. I currently have 9 cases open with seller support, trying to change back about 40 ASINs.
Getting the usual run around but even when changes back are approved there is no sign of any actual change.
Looking further I am seeing a problem, whilst the categories I use are all present on the product classifier for listing new items or changing existing ones, looking live on amazon these categories are no longer present.
These items are old fashioned nails and screws but are getting reassigned under power tools and even beauty products. wood screws as a result are no longer listed under screws or even the wider category of nails, screws and fasteners or even the broad category of hardware.
Seems Amazon are reducing the range of listing and reassigning existing products at random or by 'bot
Any suggestions how I can get some answers about this