Volume jumps since tvOS 18

On the apps Waipu and Netflix (and possibly more) since tvOS 18 the volume jumps up and down. Mostly it's down (maybe by 10 db), though sometimes, for a short time, it is as loud as it should be. The latest update of tvOS did not help. In other apps the volume is too low too, though I haven't noticed the jump to the actual, regular volume.

I'm using an ATV 4K 3rd gen going into a HD Fury Arcana going into a Samsung S95C. All via HDMI 2.1 cables. From there audio goes via eARC to a MiniDSP Flex HT, which in turn connects to a power amplifier.

I know of at least one more case where since 18 there have also been such issues with Waipu, though that person did not mention Netflix.