Found another issue with reminders where they were orphaned hence not allowing to execute any action except dismiss. With latest fix snooze and open work properly, snoozing the reminder and opening original calendar entry. Snooze works only in relation to pebble, not relaying information back to the phone yet - that part is not covered/documented in the libpebble so I'm currently reverse-engineering the protocol. Already found the way how to extract required info but still not clear what are options which are driving this particular reply format.
To get current calendar entries fixed would need to use Reset Timeline button to re-populate calendar to the timeline.
So new timeline9 beta now looks like a good candidate for another pull request.