Recorded Webinar playback has continual menu popups on IOS devices

I'd like to use Recorded Webinars, but our users on iPhone and iPad see the bottom popup menu activating and deactivating throughout the duration of the webinar.  It occurs when using either the most current Safari or the most current Chrome. It is not caused by accidental user activation since it occurs when the device is untouched on a desk. I have not seen this on OSX , Windows, or Android in any browser.

The effect sometimes takes several minutes to begin, but once it does it continues throughout.  The dark, semi-transparent playback menu will, unprovoked, pop up and hold for 3 seconds (while the video continues to play behind it), then drop and fade.  The video will continue to play for a length of time between 20 seconds (00:20.00) and one minute and 30 seconds (01:30.00) then the menu will pop up again for 3 seconds. 

This occurs whether full playback controls are provided to the user or not.  When playback controls are not provided, the menu displays only the audio control and, depending on the platform, the fullscreen arrows.  The menu pops up whether the webinar is playing fullscreen or windowed.

It  then holds for 3 seconds and drops down / fades out.
Rinse.  Repeat.

I made these timings with a stopwatch today, so they're not perfect.  But I did do enough samples to understand that the menu was up consistently for 3 seconds and down for various amounts.

Is anyone else having this occur?