Tried customized and standard Xenforo style. Cleaned all caches (Xenforo and browsers) checked for outdated templates.
Function works on standard PC as designed and did work on mobile devices with Beta 3.
Tried to re-create problem on xenforo.com but function work from both mobile devices so I do not report this as a bug.
Any suggestions on steps I can take to isolate/resolve the problem?
Edit: Did installation of 1.4.0 RC1 as an upgrade of installed Beta 3