One work around for the "Player not found error" & the problems with Command blocks on spigot with Essentials. The /minecraft: is the solution for your troubles with teleportation and other commands on servers.
Keep in mind that if you convert the map to a singleplayer map, to convert also the /minecraft:XXX to normal commands or include booth from the start.
Hello I´m Meddon, Minecraft Builder and Terraformer.
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Minecraft Solo Builder
Shaders: SEUS
Texturepack: Default