I know this particular issue isn't on your guy's end but wanted to propose adding a mitigation to the code to either use the default 180px size from minotar or drop the size entirely. On a handful of avatars I've noticed the helm displays Steve instead of the character skin. I will send one as an example:

https://minotar.net/helm/40725291656b4a6e8bbb6c9448d12408
And if you have it resize to 128 then it displays wrong, but I've not seen this happen at any other size
https://minotar.net/helm/40725291656b4a6e8bbb6c9448d12408/128

Actually, not sure how I missed this but looks like there's already an experimental config for this. Will close, sorry!