Have a Sony KP-51WS510 with red outlines

In replacing the CRTs, there are multiple focus adjustments. The basic one first is the Mechanical lens adjustment on the CRTs, (in this case red), the second one is the Electronic Focus on the Screen/Focus Block on the front of the unit behind the front panel. The third focus and on of the most important is the Beam Centering Focus. (In this case RED CTR) It is located on the neck of the CRTs. They are the first set of adjustment rings up from the CRT Boards. If any of these focus adjustments are off they will cause a symptom like yours to occur. Normally these adjustments are made before any convergence adjustments are made. I would double check to see if the repairman made these adjustments.
I hope this helps
Skyassoc