On iPad Pro 12.9 (2021) the audio recorded by the external microphone sounds muffled

I have connected a Rode smartlav+ microphone to the usb-c port of my iPad Pro 12.9 (2021). I am using an original Apple usb-c to 3.5 mm headphone jack adapter to connect the microphone.

With this same microphone, the same iPad, and with the same adapter, I have recorded many videos without problems. Now I find that the level of the audio recorded through the usb-c port has dropped enormously. Recorded audio appears muffled. In order to hear it at a normal level I have to amplify the audio by 400% or 500%. I recently upgraded my iPad to iPad Os 15.2. With the OS prior to 15.1 the problem did not occur. I hope that an iPad Os update will solve this problem soon.

P.S: I've been testing to see if it's a problem with the microphone, or the adaptor. If I connect headphones to the usb-c adapter the audio is heard just fine. If the adapter was faulty, I think the headphone audio would have problems. I then tried connecting the Rode external microphone to my iPhone, using another Apple adapter connected to the lightning socket on the iphone. The recording of my voice works fine, on the iPhone, so it seems that the Rode microphone is also working fine.

The problem only occurs when I record incoming audio on the iPad Pro via the USB-C port. So I think this is a bug that was introduced with iPad Os 15.1 and has not yet been fixed with iPad Os 15.2. That's my suspicion. In fact, with previous OSes, recording with the external microphone worked fine.

Has anyone experienced the same problem?

P.S: I've also tried restarting the Ipad but I didn't solve the problem.