I can’t reproduce this one. I use AirEQ VST3 often and it’s been stable for awhile now here. Are you using the latest build 1.1.5.3 of the plugin? You can download it here:
http://downloads.eiosis.com/AirEQ/Installers/AirEQ_Premium_1153_Mac.zip
I also get the error message when trying to use the 5.1 version but I’m not certain the 5.1 should be used in WaveLab anyway. I admit that I have very little experience with anything beyond stereo routing/processing in WaveLab though.
I just stick with the stereo version and never use the 5.1 version of AirEQ.
The latest VST3 version is stable here on OS X 10.11.6