No, I don't think so. 1 of mine in both eISY's also do not have a Json file.
I just resync'ed again, no errors.
Do all of your temp data jive with the admin console or the webcontrol console?
Is the heartbeat switching between -1 and 1 every shortPoll?
Does the time/date update also every shortPoll?
I quess it would be easier to have asked, is the plugin working fine in UDM, just with the errors?