[morzh]

To answer, first: the caps should almost always be checked out of circuit. Which could just mean one lead desoldered.
Now, by ceramic you are likely meaning the mica molded caps (I have to go and look again into my chassis on the bench). Those are extremely stable, almost never are off by much. It is very strange that you have many of them off.

So,

1. Are you measuring with hands NOT touching the leads (only the meter's leads should touch the caps' leads, hands should only touch the plastic holding part of te leads)?
2. How much heat did you have to apply to desolder the caps? Too much heat could damage them.
3. How quickly after you had desoldered them did you measure the caps? You should let them cool off - the heat does affect the reading.

4. You are MUCH better off not even touching mica caps. They are almost never in the places that present the danger of damaging the power supply. In a rare case they are bad, you will quickly find out about it. I never touch them. Never have met a bad one so far.