Thanks for reporting, I want to fix the issues but have a difficult time to replicate them.
However I have an idea what's going wrong.
I assume you're experiencing the problems on the My Modular page?

The desktop version listens to keyboard shortcuts. Shortcuts like backspace delete modules, d duplicates them and so on.
If the browser enters shortcut mode, the input fields are disabled, maybe this happens on your iOS device.

I have now disabled the whole shortcut routine for touchdevices, it makes no sense there anyway.
I have already deployed what's hopefully is a fix. Check back if it improves the behaviour or not.

Beep, Bopp, Bleep: info@modulargrid.net