External microphone cuts out

I hadn't used Logic Pro in a while. When I tried to start recording vocals today, the external microphone started behaving very strangely. It's almost as if I had compressor on, when in fact I had no effects. When in silence, you could hear the ambient noise and as I started to sing, the microphone would constantly and automatically adjust its input volume; the louder I'd sing, the lower the input volume. It's as if it was trying to normalize the volume. Before you ask, my setting under the Orange Microphone icon is 'Standard' (not 'Voice Isolation')

Can you please help? This is driving me insane.

Sequoia 15.0.1.

Logic 11.0.1