That’s very strange and I can’t reproduce your issue.
Are you rendering on GPU or CPU ?
Have you tried other files as alpha maps ?
Can you upload your file if you didn’t find a solution ?
This can be a bug or your mask has some artifacts.
Share your file and textures with the development team to help them figure what is going on, and in the meanwhile, mix the sss and the diffuse with the ‘Is Camera ray’ as factor (if you need it right away)