Maybe an upgrade to Mx 7.23.8 could solve your issue? That version solved some iOS issues that are maybe related.
Release note: (link)
When running a hybrid app or web app in a mobile browser on iOS 12.2, the keyboard did not appear when clicking an input field, and you had to click multiple times to get the keyboard. This is now fixed. (Tickets 82022, 82079, 82462, 85575, 86079, 86186)