Hi Steve
We're also experiencing problems, which Mitel and SpectraLink are looking into... which have been plaguing us since our system was installed back in February.
The WiFi part of our phone system consists of a Mitel 5000 HX, Ruckus ZD1112 + 11x ZF7363, SpectraLink 8440's and Cisco SG300-28P switches. Are you much the same?
Matty.