In multiple test worlds I'm getting these messages spammed each time the world is initially loaded or chunks are reloaded containing Mekanism things. Seems to specifically affect transmitters. Log is below:

'Fixed' this last night with ac6154a. The only known scenario where we get these messages involves transmitters firing an update packet on server load too soon for clients to see. This doesn't indicate any kind of serious issue. As such, my solution was to just lower the log level to INFO; in the future we may lower the logs further to debug.