Symptoms

We have form with 4 tabs. On a small screen (especially on mobile device and in portrait mode), the third and fourth tab disappear. There is no scrollbar as well so we are unable to locate those missing tabs.
 

Diagnoses

Form is not using Lithium theme, and only the Lithium theme is designed for mobile use.
 

Resolution

There are two workarounds:

1. Change form theme to Lithium or

2. Set the Min Form Width property.

The Min Form Width value must at least be the sum of width of all the tabs. This way when the browser window is below the Min Form Width value, the form will stop shrinking, and the browser will introduce a scrollbar for users.