Thanks for the reports. I've got some optimization for the Deeps coming in the next update, but this is the first I've heard of it happening in Deep Town. I thought it was related to enemy AI but I'll rerun the profiler.
Does this happen continuously, or just for a few seconds when the level initially loads?
If it's continuous, it might just be an issue with the Chromebook not being able to render large areas, so I'll see if I can cut them up in the future.