I've been shooting "Ultrafine Plus", which seems to be rebranded Shanghai GP3, I get the same problems with numbers, spots and dots. (http://photofying.wordpress.com/2013...ultrafine-plus) I've had 40% of the rolls I've shot already show these problems.
I don't understand quite how you avoided the problem. Did you sponge the film before development? Or did you manage to clean it already in the development tank?
(I have another couple of boxes of this film and would love to be able to shoot it with consistent results.)