PowerChute not shutting down automatically when power lost during PC boot

[Anonymous user]

I have a Back UPS CS650 connected via USB to my Windows 8.1 PC in order to let PowerChute Personal Edition 3.0.2 shut the PC down (or actually hibernate) when power was lost. A few minutes later it goes to battery sleep and will wake up again when external power returns. After wake up, PC will automatically boot. That works fine. However, in one case this doesn't work.

To reproduce the problem, I do the following:

1. Take away external power for 5 minutes so that PC is in hibernate, UPS is in battery sleep
2. Provide external power again temporarily (for 8 seconds) so that PC gets power again and is booted (or starts restoring from hibernate)
3. Take external power away while PC is restoring from Hibernate, so that there is no power at the point in time when Windows continues to run
4. After Windows has restored, PowerChute shows me a system tray message that it will shut down the PC again in 1 minute. This is exactly what I want

The problem is: it doesn't do it. The PC stays on and the Back UPS runs on battery permanently. To me it seems like a bug in PowerChute. What can I do?