RuntimeError: stack expects each tensor to be equal size, but got [3, 64, 68] at entry 0 and [1, 64, 64] at entry 18


In some part of your code which is not shown in the snapshot, you are using a stack function where you stack two elements with different sizes which are (1,48,48) and (3,48,48). If you share the full code snippet, we can have a look.