I just tried to create a subset wit h a generated band. It worked with out a problem. Without resampling upfront.
So, just a few more questions.
The message above seems to indicate that you are using a valid-pixel expression which references all the other bands. Is that true?
Without knowing the data, it is difficult to make a diagnosis.
Is it possible for you to provide me the data?
I’ll send you a PM with a location where you can upload it.