This can happen if the user changes the Account id on the Interaction on Customer Service Entry. Users tend to do this believing that it brings them to the interactions for another account, but it actually changes the account id for the interaction that they were on.

Here is the correct way to navigate to another account:  users need to click the binoculars at the top (or click F3) to bring up the Find Interactions window and search for the new account.

Information on this can be found in TA help:

Changing the Account if You Selected the Wrong Account