I don't know if this is related to the ATUM Multi-Inventory or general plugin but we're having the problem that products are randomly thrown to SOLD. Our page has two languages and usually it only makes the products go SOLD in one language. I have to log in to wp-admin, choose one of the products, click UPDATE and everything is back to normal.
I had this problem with the plugins two ATUM updates ago. Then with the previous ATUM update it seemed to be fine for a while (I decided to not use the plugin at all for a while and then for the last few weeks before update I used and it seemed to be fine) and now with the most recent update the problem is back again.
The webpage is www.plummebeauty.com and if this helps, I can give you temporary access to check the issue because this is very problematic as I cannot be checking the page all the time to see if the products are available or SOLD. Also, please don't tell me to just turn all other plugins off as the problem can happen maybe once a day or sometimes even less often and I cannot keep the site not working.