I was having similar issues with Syncthing 0.14.40 between two Ubuntu servers (16.04). A ‘uname -a’ on both show the following:
Linux xxxxxxxx 4.4.0-101-generic #124-Ubuntu SMP Fri Nov 10 18:31:34 UTC 2017 i686 i686 i686 GNU/Linux
Linux xxxxxxxx 4.4.0-101-generic #124-Ubuntu SMP Fri Nov 10 18:29:59 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
They would initially connect and start syncing and then they would just disconnect. They are both on the same LAN. The 32bit server only has ‘Local Discovery’ enabled as it just occasionally backs up the 64bit server which does all the main syncing to other decices.
I stumbled across another forum discussion (Devices become disconnected) and I followed the directions regarding Enabling “Limit Bandwidth In Lan” and then setting a non-zero limit on Incoming and Outgoing rates (102400) and it looks to have fixed my issue. Just wondering if this bug has crept back in again.
Peter