Channel Groups Disappear when Channel Tag added with sort index 0

I have a number of IPTV networks with approx 10,000 channels.  When a new channel tag is created in tvheadend (or channel group in kodi), it appears in tvheadend with a default “sort index” of 0 (zero).

For some reason, this impacts my KODI clients and removes all channel groups which are formed from the tags and leaves 10,000 channels in “All Channels” with all other groups disappearing.

How can I diagnose this issue?
Has anyone seen this before?

If I this go back into tvheadend and change the channel tag sort index to anything other than 0, KODI refreshes the channel groups and all of my favourites and channel listings are grouped correctly.  This happens weekly and although I can fix it manually, I would prefer to prevent or automate a fix. I have also tried addressing this issue to the tvheadend forum.