Symptoms of overutilized NAS

I've heard that there is an unwritten limit (around 12-15) to the number of connections that can be supported on a single NAS due to single-threaded processing and queue depth on the ADCS VT100 plugin. We make pretty extensive use of RF Scanners across our organization, and currently have around 13 on our existing NAS. We're experiencing some problems (hexadecimal errors from the VT100/NAS interface), but I'm unsure if they are related to volume.

Does anyone have any symptoms that they've noticed? What kinds of errors are typical when a NAS is reaching its limit. I'm honestly astounded that limits and symptoms aren't more widely available from MS. Coming from a .Net/Win32/SQL background, almost every error code that might be thrown is documented somewhere, but I haven't found anything here.