Random Forest Classification: Error Bands of different dimensions

I am new to SNAP and I am attempting to run the Random Forest Classification on a subset from an original sentinel 2 image.
I have successfully created all of the training data, however this does not show up within the Random Forest Classifier dialog. At the bottom of the dialog, I receive this error:

Error: [NodeId: Random-Forest-Classifier] Bands in source product subset xxxxxxx are of different dimensions.

Please may I have some advice as to where I have gone wrong?
Many thanks in advance!

I think the problem is due to, the Sentinel-2 image has different resolution for each bands. When you are taking a subset, different bands may have different pixel number. So before you take the subset, resample the image with desired pixel size, for example 20 m.