Not sure what is going on and I tried searching everything up about 1.14 bugs and spigot but I've been having issues with mobs/entities despawning on my server after when I restart. So before when on 1.13.2 there was never that issue of despawning but after upgrading the server to spigot 1.14 it's been happening a lot with mobs or entities just randomly disappearing after I stop the server and start it back up even when I make sure to /save-all. I would have tamed horses named tagged or tamed wolves whether within the loaded chunks or not after restarting they randomly disappear. Even item frames would disappear. When I do not restart nothing disappears or despawns. It's happened with the first release with the spigot when first out in 1.14 then I tried updating spigot recently to the newest current version still have the same bug My guess since if 1.14 spigot is still in development there's probably a bug somewhere within it causing the issue. None of the bug seems to happen when in a single player world in 1.14.