CEF mode is no longer supported in 1.8 series - it wasn’t really developed further in 1.7 as well, because we were not happy with it.
Could you double check registry entries for browser emulation please? - Enabling HTML5 in the Windows .net Player
If possible you could also export your layout and send it to me via private message, then early next week I’ll let it run on one of our test PCs to see if it will also show high CPU/memory usage after few hours.