Rachio 3 App Freezes Often

Just purchased Rachio 3 from Amazon and installed it last week including loading the app. Was initially impressed, but then the app started to freeze. After a couple of tries I thought it might be my iphone so did a hard reset. No improvement. Thinking it was my router, I checked my other apps and sites which were all okay. This is more than frustrating. Am on the cusp of taking it off the wall, and sending it back to Amazon. Any suggestions?

Is the problem just with the app (when you open app.rach.io in Safari it works fine)?
Or with the phone (when you visit app.rach.io from a PC, tablet, spouse’s phone, etc. it works fine)?

If all of the above fail, can you be specific at what step it freezes?

A screenshot of the frozen state would be useful.

Also, is your iPhone software up to date? I’ve had no problems with either my iPhone or iPad freezing, but I have not yet installed IOS 12.4.