This was a solution found from Infomir support, it seems to have solved the sound issue...
1.Check the sound settings following the instructions below. The settings should be the same as in our message.
Go to the main menu of the internal portal, open the "settings", after 'system settings" and check the "Audio" section and after the "Video".
All the values should be exactly as we wrote to you below, then there should be no problems with the sound. If in any line, you see another value, change it the same like you see in our message.
Audio output mode-stereo
Operating mode-RF mode
Vide output mode-
Vide output mode and Graphic resolution.These lines must match the cable you connected the box RCA or HDMI and the video resolution that supports your TV.
press F1 red
Auto frame rate-Disabled
2. You can also try resetting the factory settings and update the box again. Before doing a reset, save all the necessary information for you, after factory resetting, the portals and playlists are deleted, this will need to be added again.
How to reset the settings to the factory and update the box you can find on our website.
Auto frame rate-Disabled did NOT solve issue.
I wouldn't say that the problem is completely solved as it is not a solution to lose a function (Auto frame rate) to help solve another issue...