Found the problem. When I ran the update, the contents of the Apps folder in the wwwroot was updated. But the Apps folder under eCommerceFramework/5.3/Shared was left untouched, and thus out of date. Breakage ensued.
Thanks for the tip, even in version 7.10.3 this helped me, only difference was I needed to copy Apps and App_GlobalResources from nuget package to my CommerceManager web site
I updated EPi and the EPi Commerce Manager from 7.5 to 7.8.6 on a test site. Everything seems to workfine, with one major exception concerning shipping methods in Commerce Manager.
When I go to Admin->Order System->Shipping->Shipping Methods and select a shipping method I created in 7.5 a red error message is shown at the top of the edit window: "Error during binding gateway settings: Object reference not set to an instance of an object." All fields in the editor look normal though. If I hit OK, an exception is thrown:
If I try to create a brand new shipping method, a similar exception is thrown as soon as I hit "New":
The error message in the editing page suggests this has something to do with ShippingGateways, but I have no idea what the actual problem is. Has anyone seen anything like this, or have any suggestions?