X9 lite R-XSR ACCESS uneven refresh rate

[benaresq]

After using my R9 lite for a few months, I decided to try upgrading my R-XSR receivers to ACCESS for my racing drones.

I flashed my internal module and receivers with the latest firmware and they bound up OK, but when I tested them I found the refresh rate (while fast) is uneven which appears to be upsetting the Feed Forward in my flight controller.

In the attached picture from a log file, you can see the frame rate (red line) changing from around 6.95ms to 7.12ms. While that doesn't sound like much, you can also see how the timing changes upset the smoothness of the stick movement (yellow line) which drives Feed Forward (blue line) to spike.

I've tested this on different flight controllers and different receivers using both SBUS and Fport and it doesn't appear to change.

While I can probably mask some of the issues by adding filters, I'd like to avoid it if possible. Filters will delay the FF response which is exactly what I don't want.

Could my radio be faulty or is this an ACCESS thing?