webjob failing / file not found exception / Microsoft.WindowsAzure.Storage

I'm pretty sure I understand the error, I just don't understand why and why now.

Unhandled Exception: System.IO.FileLoadException: Could not load file or assembly 'Microsoft.WindowsAzure.Storage, Version=9.3.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040) ---> System.IO.FileLoadException: Could not load file or assembly 'Microsoft.WindowsAzure.Storage, Version=7.2.1.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

Sure enough the version the web site is:

My question is that this was a running web job which ran successfully back in 2018-09-03 - why is it failing on the versioning of an assembly now?

After this time, we simply turned down the resources of the web site, and waiting for the next time the system would be used.

This year, I cranked up the resources and it's now failing! The Web.config has no reference to this file or the version - so I'm thinking it should just find the dll, but I don't know why it's referring to the 9.3.0.0 version, and why the reference to the 7.2.1.0 version?

I really don't want to take the time to re-deploy and recompile, as that will then require a full regression test - and the client will simply not pay for something that should just be running.

What am I missing?