10pF value, it would hardly do anything. Technically it should be a small snubber for the clock to stop ringing. , clock resistors I think were 33R, so 33R plus 10pF... Basically a RC filter/snubber. R21 should be a 33R or there abouts also. I would check on a scope and see whats going on there. Its a long clock run from where the clock patch is installed normally.. such a long trace will have a lot of ringing on it.
There was a guy who had all sorts of cracking noises on his Falcon, he used my clock patch and reported all the problems went away. Can't just think who it was now though.