Cometbird 9 crashes when idle

I have been experiencing Cometbird 9 crashing when I leave it for extended periods of time, i.e. an hour or more. Usually I have 3 or 4 tabs open. This has only started since I updated to version 9. Has anybody else been experiencing this?

TIA

I noticed today that I am up to version 11. I can also report that the crashes seem to be less. I hope I have not spoken too soon, but maybe the browser is stable again.