When I save file as an idml from CC2021 I cannot open it in CC2020 as it crashes. CC2019 and earlier can open idml files from CC2021. It seems to be an issue only with CC2020. I've managed to open a 1 page blank document with CC2020 from CC2021, but anything that I've worked properly on crashes when the idml is opened in CC2020. I've attached an example.