Back in In-Portal 5.1.1 we have introduced the improvements to Memory Cache Key when separate memory cache was used for each developer. Original discussion for that was Separate memory cache for each developer .
Looks like we have missed to add the Database Name to the equation for that Key which lead to the problem when multiple developers started to share the same Cache settings.
The fix is pretty simple - add the DB name to the key string.
Here is a new task for this:
1028: Missing "Database Name" in Memory Cache Key