Logging: Problems with LoggerNotifier and associated columns

[bastianilso]

If a variable changes, the change is permanent until the variable changes again. This causes some values to "flow over" into columns - it's not a problem for data analysis per se (those values can be discarded anyway), but it would be nice to clean this up.
Expected behavior:

Current behavior:

The behavior might happen because I'm using the wrong constructor for LoggerNotifier, but as this is not an important issue, we can look into this later.
This only applies to recent additions to our event logging (Pointer Hover Begin / End).