Electrostatic Deflection "Bunching" - Solved

[dtvmcdonald]

Its quite OK, indeed very excellent, to use ceramic caps in this
coupling application. Use paralleled 6KV 0.01 uF caps, usually
two of them to make 0.02 uF. Using the specified 0.005 uF
does not work well with the ceramics ... or anything else for that matter.

The caveat is that using 0.02 or higher, you have to remove or
at least tone down any circuit that is supposed to "correct" linearity
for using caps that are WAY too small.