@MadSpaniard I downloaded the mewly updated iOS app that came out a few days ago (around 01/24 or so) and now the "Turn On - Use a Preset" is working fine. So it seems Kasa has fixed the issue I...

Update: I just loaded the latest firmware v1.5.10, and deleted and re-installed the Kasa iOS app, and I'm still getting the same error "invalid argument" when I try to save a schedule to "Turn On -...

In latest iOS app v2.18.0, the ability to create a schedule on a Kasa Dimmer Switch HS220 seems to have an issue: if you set a schedule to "Turn On - Use a Preset", and select any preset e.g. 50%,...