What kind of cache do you mean?
We are using IPageDataContextRetriever to get the current page, and also we are using CachingRepositoryDecorator from Dancing Goat. For the current page, we are getting cached values as also from the repository which uses Cache attributes.
If using a custom caching, are the correct cache dependencies defined in C# code?
If cache dependency is not correctly defined, then removing cache will not work at all, but for one presentation server cache is removed but for another, it remains.
Is in Settings -> Versioning & Synchronization -> Web farm -> Allow synchronization for selected Cache option?
Yes, the option for Cache is selected in Settings.
Which hotfix version are you using?
For site A it is v13.0.51 and for site B it is v13.0.45.