In September 2017, we received multiple reports of Android Oreo 8.0 phones rebooting spontaneously when using certain Hermit features related to the newly-introduced Notification Channels feature.
We investigated and immediately reported the bug to Google, because it is not a bug in Hermit, but in the original Operating System code. Android Bug 65650999.
Google replied that they had already fixed it, and we believe the fix was made available to all phone manufacturers and to Pixel owners with the October 2017 update. While we were waiting for this rollout to complete, we removed support for new Oreo features in Hermit temporarily. After several months, we felt confident that most users would have upgraded to the latest Android Oreo release, so we brought back support for Oreo with our Dec 31 update.
Even now, many phone manufacturers have not yet offered critical security patches and Oreo 8.1 updates to their phone users. The proper solution for this issue is for your phone manufacturer to issue an update for your phone.
As a temporary work-around, disable Notifications in Hermit.
You can use all other features of Hermit without a problem. Hope this helps!