It seems these freezes I observed are related to the change of sector ownership. Whenever an adjacent controller joins or leaves, the sector ownership is automatically recalculated, which requires results in a peak performance request. During this process, ES is more or less completely blocked. So when working on tags, you basically have to pause until this calculation has been completed. When staffing a radar sector in a busy sessions, these changes might occur every minute, especially when a group of controllers or an airport is starting or ending coverage.
In previous versions of ES, this seemed to work smoother. Maybe this kind of calculation can also be moved to a separate thread, so to not freeze the visual update and other functionalities?