Slowing down on cruise control

[Ninja59]

A bit of an odd one even leaving me a bit perplexed is my car's decision on cruise control set at X, ever so occassionally it will "slow" down by X- 1mph and within a few seconds regain it, I am not sure if it is "braking" in this moment so leave that open in mind.

So far the moments I have found it does it more:

Has to be on cruise it does not appear to happen when on the speed limiter or just normal driving

More likely to happen in the rain :huh: (wipers on auto mode)

Tends to be at higher speeds 50+

No set time period, totally when it feels like it

I do have some codes:

CD0420 - Error on Flexraycontroller on Flexraybus - under ABS/DSC

C98420 - Flexray controller error on bus

Now looking on bmwfault codes the first one is under the ZGM (central gateway), the second one is the SZL (steering slip ring/column) or simply could it be the switch blocks in the steering wheel?

Another potential thought which leaves me feeling "cold" is the DSC hydro unit...but it would do it all the time not just on cruise IMO (usually being caused in the rain by the fact that the disc drying is then in operation). Additionally if it was this it would be surely at set intervals?

Either way I will be thankful for a warranty as the the SZL is pricey and the DSC hydro unit eye watering.

Your guidance will be massively helpful ladies and gents!