You need to bring in way more details on versions and platforms you are using. We can not guess. There is currently a thread in here about 0.14.40 connection issues , and I have personally used RC release candidates of still-in-development version 0.14.41, currently at RC5 version or so, it is linked right here on the forum.syncthing.net address when you browse the main overview.
Currently it links to github RC5 version at: https://github.com/syncthing/syncthing/releases/tag/v0.14.41-rc.5
You might try that one on one of your nodes and see if it helps that node and its neigbor nodes. Depending on how complex your infrastructure is, syncthing link wise, you might need to add more RC5 versions or newer or later ones, or revert back to even 0.14.39 to get better results for the moment.
Hopefully release of 0.14.41 will sort this out or at least improve.