Conversion Failed in server

When I am starting a snapshot server on my pc (15W32B) and I load in an AMPLIFIED world from Minecraft 1.8.8, I get this error, after the error the server just quits and closes.

[18:54:28] [Server thread/WARN]: Encountered a problem while converting the player save files, retrying in a few seconds
[18:54:33] [Server thread/ERROR]: Conversion failed, please try again later
ly$a: Could not convert file for Ghrane
at ly$6.a(SourceFile:329) ~[minecraft_server.15w32b.jar:?]
at ly$6.onProfileLookupSucceeded(SourceFile:310) ~[minecraft_server.15w32b.jar:?]
at com.mojang.authlib.yggdrasil.YggdrasilGameProfileRepository.findProfilesByNames(YggdrasilGameProfileRepository.java:59) ~[minecraft_server.15w32b.jar:?]
at ly.a(SourceFile:56) ~[minecraft_server.15w32b.jar:?]
at ly.a(SourceFile:347) [minecraft_server.15w32b.jar:?]
at kp.aT(SourceFile:530) [minecraft_server.15w32b.jar:?]
at kp.i(SourceFile:164) [minecraft_server.15w32b.jar:?]
at net.minecraft.server.MinecraftServer.run(SourceFile:422) [minecraft_server.15w32b.jar:?]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_51]
[18:54:33] [Server thread/WARN]: **** DETECTED OLD PLAYER DIRECTORY IN THE WORLD SAVE
[18:54:33] [Server thread/WARN]: **** THIS USUALLY HAPPENS WHEN THE AUTOMATIC CONVERSION FAILED IN SOME WAY