Microphone Failed Result=33

We're currently working on an app which uses the Microphone to record the user and plays back their recordings. Recently we have had a strange error being reported on PC and Android.

Android,error,"Starting Microphone failed. result=33 (An error occured that wasn't supposed to. Contact support. )"

We are making sure to authorise the microphone before starting the recording, and we're not really sure what is causing this bug. We were just wondering if anyone else has seen this bug, if they know how to reproduce it and ultimately fix it.

Thanks and all the best,

David.