this might be a sample rate issue. SessionLinkPRO works at 48kHz internally and uses sample rate conversion if fed with anything else than 48kHz. Some audio interfaces - or more precisely the drivers of the interfaces - seem to have problems with the conversion.
Please check your sample rate in OS X Audio-MIDI-Setup / Windows Sound Settings for the M-audio, both at playback and record. Also, if the M-audio is not the default interface in OS X Audio-MIDI-Setup / Windows Sound Settings, please check the sample rate for the default interface, too. If not at 48kHz, please change the devices to 48kHz and restart Chrome.
Please come back to me if this doesn't help!
A short notice on mobile use: currently, we do not officially support using mobile devices with SLP, though Android and Windows device normally work pretty well. I cannot exclude the mobile device being responsible for the pitch so maybe also try a connection between to computers. This can even be done with one computer and two Chrome tabs, one for master and one for the guest. Please turn down your speakers to avoid feedback loops!
Tim | SessionLinkPRO