There appears to be a problem with converting user statistic files with the game server on upgrade from 1.7.x to 1.8.

Initially, I did a 1.7.2 server migrate to 1.8 and noticed a ton of the following in the server logs:

[WARN] Invalid statistic in ./world/stats/<uuid>.json: Don't know what <stat item> is

I also found all users lost their blocks and items stats, but general and mob stats remained.

Through testing I found that single player stats will convert properly from the old user.json to uuid.json if you start with a 1.7.x version earlier than 1.7.9, then run 1.7.9, then 1.8.

However, if you have a pre-1.7.9 server, update to 1.7.9, login so the server converts it from user.json to uuid.json, then update the server to 1.8, the stat file looses the item and block stats.

I've tried going from 1.7.2->1.7.9->1.8 with single player and had no issue. Also did 1.7.2->1.7.4->1.7.5->1.7.9->1.7.10->1.8 and the conversion works for single player maps. But, for servers, it fails.

Clients tested were on Windows7x64 with java 1.8 latest. The server is a linux x64 ubuntu14 with oracale java 1.7 update 55.

I doubt this could be a java outdated issue, but am going to update that and run more tests to rule it out.