This is the thing - I don’t use tripods and want to use the waist level finder. It’s why I have the camera.
Anyway suggest check your system first to eliminate system fault. if you can get sharp focus using tripod follow proper process, then it is the way your capture method matter, try to find the way suit for you to improve performance. otherwise service gear I am afraid.
suggest using winder if use with 503CW, I found it will hold camera much more sturdy and using mirror up if possible with minimum shutter speed 1/250 or 1/500 vary with kinds of focal lens. anyway I can get sharp image sometimes using 1/60 to 1/125, but that is not look always so lucky.
another thing is try using screen 42215 or 42217 ( 42215 - Acute Matte D - prism, split or 42217 - Acute Matte D - prism, split, grid ), if using with CFV 50C II , There are a good screen come with the back. I always turn screen 90 degree keep vertical installation rather than default horizontal installation, as my experience I like the split line vertical to focus the target eye if for portrait photography. it is easy to get focus point. If using screen come with CFV 50C II, I have no experience.
it is best to using 45 degree prism with correct diopter if you wear glasses for handheld photography combine with CW winder if using 503CW OR 503CXI, which is sturdy even though concern about the weight.
Below pics captured ISO 100 1/60 CFE 40 IF@F8 Phaseone P65+ handheld By 503CW CW winder mirror up then release press shutter, no sharper
Sorry for post phase back pics here, just want to demonstrate handheld somehow still can get sharp pics. thanks
Edit again with switch off calibrate CA in C1
100% central, you can see strange purple CA, the reason is C1 produced when apply calibrate CA
below 100% sample can not notice any purple CA, switch off calibrate CA in C1
Below pics captured ISO 50 1/125 CFE 40MM IF @F8 Phaseone P65+ handheld By 503CW CW winder mirror up then release press shutter, no sharper
Below pics captured ISO 100 1/125 CF 250MM SA @F5.6 Phaseone P65+ handheld By 503CW CW winder mirror up then release press shutter, no sharper
it is comprise with portable and sharp image. Can get both sometimes.
as you see, the highest iso I chose is iso 100, due to p65+ is not good at high iso compare with CFV II 50C which can easily go up to ISO 1600 still get good acceptable image.
For P65+ the highest iso I would to use is iso400 which is the maximum I can accept. Forget about the plus+ function for 2 stop increase ISO, I found totally unusable, too grainy.
So you have much more chances than me to get good pics when handheld in theory.
otherwise there are another IBIS medium format system such as X2D or Fuji GFX which can choose if you still can not get good result I hope.
Hope this is useful.