through hole soldering vertical fill problem ground and pwer planes connected points
You mention the plane connections on the top and bottom are through "spokes", by which I assume you mean thermal reliefs. It sounds like you neglected to also use thermal reliefs on your inner planes, and as a result, that's where all your heat is going.

The only holes in planes (outer or inner) that shouldn't have thermal reliefs for hand or wave soldering are vias, which have plated connections.

This is not normally an issue for SMT boards, where the entire board gets heated to soldering temperature simultaneously.