I don't think there is a fix for that, we get it all of the time too...

Make sure the switch is act switching every night if its a large site.

there were a few problems using the telnet recently, they are all fixed according to product support in the new Lw34 software. now the logs actually show who connnected and even what port they connected to if they use the ethernet for smdr and acd realtime events

You can also install an IP serial port terminal server (i.e., something like a Xyplex) on the maintenance port of 1 (or more) of your peripheral nodes (or DSU nodes) and then give everyone who uses this their own specific IP address to telnet to. By using the maintenance port of a peripheral node it works similarly to logging into the main controller in that you always log in to the active plane and you won't have this "exceeded sessions" problem because only one person at a time can log into a terminal server (hence you want to have more than one). The Xyplex terminal servers we use also have session limit timers as well as deadman timers so no one can monopolize a port.