NOTE! Due to big internal changes to Minecraft code and the way item serialization changed in this update, once item are loaded into 1.20.5/1.20.6 from older versions cannot be loaded back into pre 1.20.5 versions. So make sure you only sync 1.20.5/1.20.6 servers and not with older version as items saved with 1.20.5/1.20.6 will be unreadable with older versions and will lead to items being lost.