The LogFilter agent properties are set with "Recycle Messages After (seconds)". While reviewing the agent data, it can be seen that it captures the same event after this period, yet since the previous alarm exists, no new alarm is generated.
This is by design. Until the previous alarm is cleared, a 'duplicate' alarm cannot be issued until the previous alarm is cleared.
One can schedule the rule "Clear Old Log Filter Alarms" to run at a certain period of the day by setting the rule to a specified schedule.
The attached doc highlights the changes required for the rule to trigger properly on a selected schedule.