Most likely your model didn’t adapt itself to the new number of classes. Since the new dataset contains less classes than the one the model was pre-trained on, you won’t get an out of index error.
However, you are “wasting” model capacity, since the majority of the output neurons aren’t used (neurons corresponding to class26 to class195).
I would recommend to change the last layer corresponding to the new number of classes as I would guess you’ll see a performance boost.