There are multiple issues how host availability is handled:

1. error message is not updated for already unavailable hosts. The error message might be changed, but it's ignored if the host is already unavailable (regression).
2. when proxy fails to send host availability data to server it does not revert internal host availability cache and this availability update will be lost.
3. the internal host availability cache is stored per process. That means with active passive proxies each trapper has it's own host availability cache and the same availability data could be sent to server multiple times.