Problem:
Uncontrolled 
Syncthing *sync-conflict* for all or many files.
Background:
I had three devices setup with syncthing for maybe a couple years now.  I accidentally 
sudo rm -rf / my laptop.  YES, true i fogort that damned period in 
./ while on my SD-Card which i was trying to purge.  I quickly Ctrl-C, but it was too late – what a disaster!  Fortunately 
~/ and my external USB Disk stayed intact for the most part.  But I had to reinstall Xubuntu from scratch.  After reinstalling 
Syncthing, the syncs kept causing many many sync-conflict files.  These were mostly for large 4GB video files and conflict creation was rampant and uncontrollable.  My syncs are all in my 
~/SYNCfolder, so I kept performing  
find ~/SYNC/ -name "*sync-conflict*" -delete (after analysis that the originals were good of course), but the conflicts repeatedly resurrected.  Some searches were suspect, and some solutions only worked for text files – worthless.
Tentative Solution:
I found the idea of a “database reset”  referenced in a github issue, so i looked it up:
-reset-database
Reset the database, forcing a full rescan and resync. Create .stfolder
folders in each sync folder if they do not already exist. Caution:
Ensure that all sync folders which are mountpoints are already
mounted. Inconsistent versions may result if the mountpoint is later
mounted and contains older versions.
I performed  
syncthing -reset-database on all three devices and so far the conflicts have subsided with the exception of a couple files.
Whew, continuous uncontrollable disaster #2 averted.  As for disaster #1, i’m still repairing that one.
As always, Good Luck!
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