So, your piano has now been properly regulated and accurately tuned. You now want to know how to check for voicing problems. I didn’t know how to really go about it properly, so I went looking for enlightenment on the Web. It’s amazing what you kind find there.
On the Renner USA web site I found this article: Voicing the Renner Hammer, by Rick Baldassin. The voicing techniques pertain to the Renner Premium Blue hammer, and may not apply to the hammers in your piano (note the caveat). But what was really useful was the information on how to check if one or more of your hammers require voicing.
And just in case I didn’t make it clear enough, your piano must be in good regulation and properly tuned first. If not you might be wasting your time and your money calling the tech in to fix a non-existent hammer problem.