[Rickertsen2]

Before passing into the PIC, the analog inputs pass though an RC filter and no other buffering circuitry! I have not measured the values of these components but it is possible that the minuscule amount of current that makes it though a 100k pot doesn't have the OOMPH necessary to rapidly change the input value and overcome the RC filter. The RC datasheet recomments 250-100KΩ resistors and in the example diagram uses a 10KΩ. Now if we look at the PIC datasheet, in big bold letters on page 220: The maximum recommended impedance for analog sources is 2.5 kΩ.. My guess is that it is quite OK to go above 2.5Ω but as you do, your accuracy goes down. The rated accuracy of the AD converter is 1/2 bit.

Btw 100K pots are required for the OI because it measures the current that flows through the pots. I believe it does this so that it can tell when joysticks are disconnected. The RC on the other hand measures the voltage that is input to it. Pots are used as voltage dividers for the RC but current regulators on the OI.

If i had designed the RC, i would have put some sort of buffer circuit in place to make the inputs less subject to impedance.