Solution:
Use MX Player as the default video playing application WITHIN Kodi/XBMC/SPMC/DBMC
Download
https://www.dropbox.com/s/hde28ih4c02dujn/playercorefactory.xml?dl=0 (you can just close the login window that appears there) and copy it to your DroidBOX device.
Open ES File Explorer, locate the XML file and long click it, then select Cut.
If you're using Kodi, the file needs to be pasted (placed) in:
Android\data\org.xbmc.kodi\files\.kodi\userdata
If you're running SPMC or DBMC, please put it here:
Android\data\com.semperpax.spmc\files\.spmc\userdata
If you have version 12 or 13 (Frodo or Gotham) of XBMC, please put it here:
Android/data/org.xbmc.xbmc/files/.xbmc/userdata/
To see the directories that start with a full stop in their name, expand the TOOLS menu on the left and turn on the HIDDEN FILES option.
Reboot for good measure, and if done correctly, Kodi/DBMC/SPMC/XBMC will use MX Player (the free version) to play all videos. You'll lose the subtitle and bookmark feature, but will at least be able to see the whole video.
If you don't have MX Player installed on your device (possible on a few very old X7 or iMX6 units), then open Google's Play Store app -
https://droidbox.co.uk/blog/faq-2/googles-play-store-signing-in-and-auto-updates/ - and install MX Player (the free version) from there.