Error Message on Multi Site plus some glitches

1) There is an error message that displays when I add or edit products in this multi-site WordPress/WooCommerce store. This is the error message: The backup of this post in your browser is different from the version below. This will replace the current editor content with the last backup version. You can use undo and redo in the editor to get the old content back or to return to the restored version.
2) I think there are other issues on this site also. I have these products for sale on two sites. and They are the two main websites in this multisite installation. There are a few other sites, but I am not using them yet. When an item sells on one site, it reduces the inventory on that site, but does not reduce it on the other site. For example, there is a product called Blank Bottle Carriers which are sold by the case. There were 20 cases available. 7 sold on one site and 2 sold on the other. However both sites are tracking inventory individually. Neither site reduces the inventory when a sale occurs from the other site.
3) There appears to be SEO problems where Google is not able to index the sites or at least not index all of the pages and products. I think something has gone wrong with the structure of the multi site.
4) Possible hacking, I noticed that people were able to create sub domains and register as users of some crazy sounding subdomains which should not have existed. I have deleted those users and subdomains, but am concerned about people hacking into these sites.
Your team has the most knowledgeable people I know for fixing Multi-Site and I appreciate your help. Thanks in advance for any recommendations or solutions to these issues.