On three separate occasions, Syncthing had deleted all the files contained within various subfolders, while leaving the folder structures untouched. Thankfully, I had backups.
I have connected my PC to android. I have only local discovery on.
If anyone has any potential explanations and solutions for this behavior, please share them.
I found this in my log file. This may help.
TLS handshake: tls: first record does not look like a TLS handshake