WIChix

Spent the afternoon getting my 301 ready for a new quilt project:

brushed out lint, including under the feed plate
oiled, including the bobbin raceway
changed needle (double checked height of needle and flat side left) These are schmetz 130/705 aka 75/11
cleaned upper tension discs
adjusted upper tension so threads are locking in the right place
mounted walking foot
adjusted needle bar pressure for even feed
doubled checked bobbin orientation in bobbin case
changed top thread, double checked threading, needle right to left

started sewing samples (diagonal seams to join 2.5" squares to 2.5" strips)

and she's skittish at the start of the seam, either not feeding through (not catching in dogs?), or clotting up at the beginning of the seam on the bobbin side. Double checked, I am starting with the bobbing thread guide at the top of the stroke.

Aack! What am I missing? (A heartfelt thank you for your help!)