Shopify to eBay sales channel sync issue overselling

[oddfaery]

hey, so pretty much since I've started my eBay, I've had this issue. I'll either;

1. Have an item sell via Shopify

2. Delete an item that sold outside of program (early on)

3. Set item quantity to 0 in Shopify for items that sell outside of program (current)

For any of these 3 options, the item will occasionally suddenly resurrect itself at some random time and sell on eBay. I thought I was going insane and just somehow having false memories of marking things sold, then I noticed one day, 2 items on eBay that were active that sold ages prior, and I went into Shopify, and the QUANTITY WAS STILL 0!  I immediately messaged eBay channel support and they said there was a sync log error on one and a failure on another?... 

I asked how to prevent it, they said it was out of their control. I asked why it happened, they said the eBay quantity would just sometimes override the Shopify adjustment. I asked if they could track all sync log errors and failures so I could prove the error to appeal the defect....it was a resounding no. I had them check specific items, they said there may have been an error but they only keep data for 14 days. 

Does anyone know a better way to check adjustment history on Shopify OR eBay? because no one is willing or able to help and history provided doesn't have the answers.

I'm at the end of my rope and my eBay shop has been completely destroyed by these defects