Nice work!
The soldering on the pre-assembled portions of kits is often pretty lousy, IME.
The Heathkit color set that I put together this year had several melted wires, dropped solder blobs, a broken terminal strip, and an unsoldered connection in the high voltage module.
I also have a Heathkit frequency counter in my shop that was factory assembled (SM-2420). I got it really cheap because it wasn't working due to several cold solder joints....