RCF EVOX class D output issue

[NoisyIndividual]

Hi, this has me stumped, not sure what's going on.
This is an RCF EVOX 8 module that is distorting on output.

The module is a Sub driver, so it is LPF'd and drives a 4 ohm speaker.

It distorts when driving a load, without load it does not distort.
I can't find schematics for this particular board, but it uses a IRS20955 chip driving 2 x IRFB4229 Mosfets.
I have changed the Mosfets, but that made no difference.
I think the output topology is going to be basically what's on page 1.
https://media.digikey.com/pdf/Data Sheets/Infineon PDFs/IRS20955(S)PbF.pdf
Attached here are 3 scope shots of the output with 5.7 ohm dummy load, 8.3 ohm dummy load, and no load.
It sounds pretty nasty with a speaker, as you can imagine.
I don't know what the scope images are showing, is this generated by the IRS chip which may or may not be faulty?
I don't see any current sense resistors, nor are there any in the Page 1 schematic.

I'm curious as to what is actually going on here.

 

[Khron]

They likely don't cost much, so i'd say it's safest to replace the chip too.

 

[NoisyIndividual]

The IRS20955 is obsolete and not available from the major distributors, but I have just discovered the IRS20957 is available, and seems to be a drop in replacement in most cases.
Probably worth a try, power supply on this board is 12v.

https://www.infineon.com/dgdl/an-1141.pdf?fileId=5546d462533600a40153559a1f4710e0