Dropdown lists fail on iOS after required field warning is triggered

Is this a return of the Adobe Acrobat Reader bug for dropdown lists on iOS? See also: New Adobe DC works not with fillable Documents (Drop Down Lists) in iOS

Issue: dropdown lists fail to show dropdown menus after a tap on Submit button has triggered a Required Field warning.

Form set-up:

• Form design done in Adobe InDesign, PDF saved as Adobe PDF (Interactive)
• One drop down list, that is set to "required", amongst a number of other non-required fields.
• Submit button (PDF via email).
• Adobe Acrobat Reader Version: 17.06.12
• iOS version: 10.3.2

Issue replication:

1. Do not select a value from the required dropdown list.
2. Tap Submit button. A warning popup message appears "At least one required form field is unfilled. Fill all required form fields prior to form submission".
3. Click OK.
4. The required field comes into back into focus.
5. Try to select a value from the dropdown list.

Expected Result: User can select value from dropdown list, and return to Submit button to successfully submit the form.

Actual Result: Dropdown list no longer works, tapping it results in no action, no dropdown menu appears.

Workaround: Clear Form, start from scratch and don't forget to select a value from the required dropdown list.  (considering the form contains over 100 fields, that's really not an option).

Additional workflow information:

• Forms reside on Google Drive.
• When accessed the user will open the form and choose Copy to Acrobat to complete the form (which opens it up in Acrobat).

For testing purposes I've also tried:

• I've added a second dropdown list next to the required one and it displays the same issue, after the warning popup message appears. E.g. NO dropdown list will work after this.
• I've also tried to see push the form to Document Cloud: Identical results.
• Testing setting the 'Required' field in Adobe
• Testing the form in desktop version of Acrobat Acrobat Reader for Desktop displays no issues.
• Updated iOS to 10.3.3: Maybe my imagination, but that seems to make the issue worth: dropdown lists fail from opening of form in my test.