Keh is a good option to start, if they really do the testing. A full service is not that complex as long they actually take things apart and clean them out as opposed to just squirting lighter fluid into the works.
Zacks Camera Repair does good work as does Certo6. Another good option is Ken Ruth at Bald Mountain Camera Repair. Of course, these are nowhere near as convenient for you as KEH. If you do decide to use any of them, call them and explain what you need. This will certainly help reduce misunderstandings.
As for Certo6, you can read junk about anybody on the internet. In fact, if you believed everyone's BS you would never send a camera to anyone for repair. I have worked with Jurgen (Certo6) for a very long time. Aside from being occasionally grumpy he is an exceptional technician and well worth the time and money for his services.
If everything seems to work you can easily test the camera without doing anything, even if it has some pinholes in the bellows. Toss a dark cloth over the bellows and take some pictures using some standard 120 color film. Try out different apertures and shutter speeds. If a shutter is dying it is commonly the slow speeds that go bad first. If that test turns out good then you can try fixing the pinholes like bernard l explained, however my experience with those plastic, Agfa/Ansco bellows shows that is only a very temporary repair. Of course, if you don't intend to use it much the dark cloth will work for a very long time.
EDIT - For the record, pre war Agfa folders use leather bellows and normally work pretty reliably. I have several that have working shutters, aperture settings and focus. I think the problems probably started post war because of cost cutting. Surprisingly though, once the issues are serviced they are exceptionally reliable cameras.