Looks like this is a pressurized portafilter? If so, they are designed to be much more forgiving with larger grind sizes, but too fine a grind can still restrict flow. I would try a courser grind first. If that doesn't work, descale the machine.

Longer term, I would suggest switching to a non-pressurized portafilter and a burr grinder. You'll get much more consistent (and much better tasting!) espresso.