I know this was probably never intended to be used together, but gaborish doesn't play nice with -d 0. If I execute:

$ cjxl -d 0 --gaborish=1 buggie.png buggie.jxl
$ djxl buggie.jxl buggie_roundtrip.png

And then with this image comparator utility:

$ imgcmp buggie.png buggie_roundtrip.png --count --write-diff-image diff.png
different pixel at (42, 0), rgba(0, 0, 0, 0) vs rgba(1, 1, 1, 0)
number of differing pixels: 2677

Here is the original:

The result of imgcmp (original image with half-transparency and difference in red):

Environment

• OS: Linux
• Compiler version: GNU 15.0.1
• CPU type: x86_64
• cjxl/djxl version string: JPEG XL encoder v0.12.0 2a4f12b [AVX2,SSE4,SSE2] {GNU 15.0.1}

Additional context
Might be related to #3458, but with an easier reproducer.
I did check that it roundtrips without errors if I remove the --gaborish=1 flag.