I am playing with quite a few mods so there may be some issues, but I'm getting the morph of just about every zombie I find. I have 20+ zombie morphs, and they all look the same.

As Morph has just been rewritten and released for MC 1.16.5, I am clearing the issue tracker as I have not provided any support Morph for 1.12.2 and earlier. My apologies for not addressing your issue.

Hello, I'm also having this issue, if you give me your mod list that would help because then I could compare what mods we have the same of!

My issue was potioncore.

I don't really know a workaround with it's specific data, but I would remove potioncore if you are sick of this morph issue.