tamte

you can add and check "allowmotionblur" property, then it will work

moo
I'm moving a 2 point line using keyframes. I'd like to take those 2 points along with the same 2 points from the previous frame and create a 4 sided primitive.

instead of solver you can use TimeShift SOP, you will also get realtime updates that way instead of having to recache if using Solver SOP

you can use Retime SOP
or Time Shift SOP