Drain mode is activating automatically and stopping my function app from running

Hi,

I have a function app triggered by an IOT hub incoming message. It works well, until recently when suddenly it stopped running. Checking the logs, I found "DrainMode mode enabled", which stops the listener and makes my function app do nothing.

Googling around, it seems this is meant to run for automatic scaling, with the idea that if the load is low it will stop some instance of the function app. However, it's completely stopping it all for me.

I have no idea why this is happening, or how to keep my function executing. I saw there was a "scale out" option for the function app, so I disabled it, but it doesn't seem to have helped.

Could I please get some kind of direction on how to stop this drain mode bring down my system, please?