"Phone is critically full" error message when recording video directly to iXpand

I bought the iXpand for the sole purpose of recording live video and audio directly onto it, since my phone doesn’t have enough storage space. When I start to record video with it (yes, using the little camera icon in the app), I immediately get a message that says my phone doesn’t have enough storage. I can close the message and keep recording but after a couple of minutes an error message pops up and it stops the recording. Yes my phone is REALLY full but that’s why I bought the iXpand! When I look back at the videos they are stored on the iXpand drive and not on my phone - why is my phone not allowing me to record directly to the iXpand? 

this is a limitation of iOS. Pictures can be taken directly to a storage device connected to the lightning port however due to iOS limitations video must first be captured to the iOS devices internal memory. Once the video is complete it will be transferred from the internal memory to the external storage device. Unfortunately due to this limitation you would need to free up some internal storage space to shoot video even using the iXpand in app camera.