I made a face that would display correctly when run in the emulator in CloudPebble. I constructed it such that it would work on Pebble Time 2 and Pebble Round 2. I could run the emulator for one format or the other and it worked.
When I went to publish for both faces the emulator run to generate the sample faces failed on the round format. It would not load and run in the emulator.
I tried various things like closing and re-opening the project, closing the CloudPebble page and re-opening, closing the whole browser and starting again. These did not fix the problem.
I decided to publish the two versions of the same code separately. Again there were failures in the publish screen but eventually I was able to publish the two versions separately.