7E101 firmware bug? Noise Gate when using USB C to 3.5mm cable

On the latest firmware for AirPods Max (7E101) I am experiencing audio quality issues when using the USB-C to 3.5mm Audio Jack (A3299).

I am connecting the AirPods Max to the cable and using a 3.5mm to 1/4 inch TRS adapter to plug into the headphone output jack (specifically designed to use headphones) of my guitar amplifier. The amplifier is a Henriksen Bud 6.

When playing the guitar, the audio signal is distorted and there is a noise gate like effect where the volume is soft and then at a certain input threshold becomes very loud suddenly.

When using sennheiser hd280 pro headphones, the 3.5mm to 1/4 inch trs adapter, and inserting into the headphone jack of the amp there are no issues at all.

Apple support recommended resetting the AirPods Max. This improved the distortion but the noise gate is still an issue.

I’ve tried this at various combinations of volume on the headphones and on the amplifier and on the guitar.

the headphones and cable are brand new and were purchased in an Apple Store within the last week.

I believe this is a firmware bug and have had issues reporting it.

the cable and headphones work fine when plugged into a laptop, I think something about the impedance of the amplifier’s headphone jack may be causing this? Perhaps it is able to drive headphones harder than a laptop headphone jack.