Unified Service Desk app not loading updated custom assembly

Hi everyone

We are using USD 2.2 with CRM 2016 SP1 on-premise. We have a custom assembly which we deploy to USD using it's Customization File feature

I have a situation whereby the USD application is not loading an updated custom assembly and keeps trying to load the old version. 

Everytime I start the USD app, it comes up with an FileNotFound exception because it cannot find the old assembly file.

So far I have tried everything I could think of in terms of deleting/disabling caching on the browser and the USD app (USD->User Settings) to no avail.

Can anyone think of anything else?

Any help is greatly appreciated.

Regards