Below is a link to a tutorial on how bad ceramic capacitors are regarding holding their capacitance value under voltage bias. Basically the smaller the capacitor (physically) and the larger the voltage across it, the less the actual capacitance will be. I have always know this to be true but I didn’t realize it was as bad as describe below. This was a good reality check for me to make sure and select capacitors for a design carefully!

https://www.maximintegrated.com/en/app-notes/index.mvp/id/5527