P: Thick red/blue banding in brightened shadows of Denoised DNGs

the test is really really simple, you download the file i linked from DPR, as i said is an underexposed photo (it's used for latitude test/shadow recovery). i don't apply any setting or preset. you convert the RAF in DNG, you add later +5EV to check the shadow recovery ability. the RAF looks fine, the DNG is broken with red patches

i am not talking about colored noise, but about the large red rectangles apparent in the DNG

here you can see the comparison DNG vs original RAF (both at +5EV)

I suspect a bug with the M1 GPU or maybe Sonoma 

i sometime have problems of 'ghost' images prodced by enhance photo function with RAF files (i use a Fujifilm X-H2) you can clearly see the problem processing this underexposed image from DPReview.

Lightroom 13.5, SOnoma 14.6.1 on M1 Macbook pro

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enhanced photo:

and the standard result:

 When trying to Denoise photos using the ai tool in Lightroom classic on my new Apple M3 Max MacBook Pro, I found that it processes the photo really fast compared to my older MacBook.. but leaves a checkerboard like color error on the processed image. I've never seen anything like it and tried to disable GPU in settings to see if anything changes and it made no difference. I take nightclub photos so being able to use the denoise tool is incredibly important to me. I thought maybe it was my camera or lens I used that night so I opened the catalog on my older MacBook (2018 2.9ghz 6 core intel i9 w/ Radeon pro Vega 20 4gb) and there was no checkerboard across the exact same photo when processing it. What could be causing this? My new laptop is under warranty, should I have it replaced? 

Updating status - adding bug

I've been experiencing this same issue. I see that I can still downgrade to 13.2 - Has anyone tried this yet, and if so have you had any issues with the catalog?

I don't know. The blocky stuff is also present in lighter areas like above the display case where there is clearly resolvable material. They're both pretty bad though and not really usable. The color blocks are extremely objectionable indeed

I'd argue your Topaz example is the preferable version. I'm not expecting miracles in such deep shadows—it's mostly noise. It'd be nice not to have dreamt-up colours, though. 

P.S. interestingly Topaz also completely messes up this file. Using denoise and sharpen and dng output in Topaz PhotoAI gives this:

I've noticed these blocky artefacts in Topaz' output in other low light images before so no surprise but we are really at the limits of the current technology here apparently...

Again, I must insist this isn't an extreme ISO image (640). It's a photo with extreme exposure and shadow adjustments made in Lightroom. 

I was able to recreate it using a different and much older fujifilm model (X-T2). That raw file is attached above in one of my replies. 

Perhaps it's an artifact specific to X-Trans sensors? Frankly, I wouldn't be surprised by that given the decade of complaints with how CameraRaw treats those files.