I have reported this bug to tizen team but I want to share it with you
If you have application with only one form and the form is set to horizontal mode only, then trying to show the OptionMenu for the first time result in a bug.
After you click the menu hard key for the first time, the OptionMenu is shown at the left side of the form and if you try to click on it, it goes invisible
Clicking again on the menu hard key will show the OptionMenu on the right side of the screen and it works now. It seems that the OptionMenu cannot detect the orientation of the form at the beginning .. It always behave as if the form is in vertical mode
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update:
I just found out that this bug only happens when the form logical dimension is set to 480 and the OptionMenu has MORE than 3 items!!