With the S905 and S906 chipsets the good thing is that basically every box with the same amount of memory and same Wi Fi chip will be compatible for a firmware donation.
You can also try a wipe and factory reset from the recovery console if you don't want to flash a firmware.The most annyoing part howver was that the remote did not provide the stop function.All player buttons olny pause the video or skip it by 15seconds.As I only have the standard 2/16 box I will focus only on that model but the procedure is the same for the others. Don't just download the image for the firmware alone as it won't work.A double click on the folder symbol next to the name will open the files contained within. If you have not done so then now is the best time to consider a backup!!!!