Try this trick I mentioned in another thread.

Use the edge of a saucer to level and strike off the excess in the VST basket. This will leave a concave surface dipped down in the middle, before tamping.

VST baskets are "flow optimized" and flow evenly all the way to the edges. The theory goes that this evens out the flow.

Whatever it does, it seems to work.

I assume you have a naked portafilter. Describe how its drips form and fill out the bottom of the portafilter.

Have you checked the pressure isn't over 9 bar? If not, do so. One less variable.
Nutating or not mutating is not the problem. It is a special technique used for a special reason. Should not be necessary unless your trying to look fancy.
Have you installed a preinfusion PID? If not, and you can afford to, do so. One less variable.
Do you see the screen on a dry puck or have a mushy wet puck?

Stay with the VST basket.

Check the OPV, buy a naked portafilter and post some photo.

Consider adding a variac or dimmer to the pump to get manual preinfusion/slow pressure ramp.