Uncommanded RC activity with Spektrum satellite and Pixracer

I was flying my quadcopter in Auto mode. It was flying between waypoints uneventfully, when all of a sudden it started yawing, and pretty quickly went into RTL. It kept yawing until just before it landed. Looking at the dataflash log, it appears that the RC channels all went totally crazy, and continued doing so until after the quad landed. The channel that controls flight mode also was fluctuating, and I was lucky that it ended up in the RTL mode. (See the attached log screengrab) The throttle channel (RC3) was fluctuating really fast, while the others were changing less quickly.

I am using Copter 3.4.6 on a Pixracer. For the RC control, I am using a Spektrum DXE and a Spektrum SPM9645 DSMX satellite receiver.

Has anyone observed this scary problem before? Is it likely to be a hardware or a software issue? Looking at some posts on this forum, it seems that there was a Spektrum/Pixracer related bug that caused erratic channel activity. Copter-3.5.1-rc1 is available for beta testing
However, it supposedly was created and subsequently fixed in subsequent releases of Copter 3.5.0 so it should not have been a problem in the release I was using.

I don’t have Spectrum gear but I do have 3 PixRacers. Why are you using 3.4.6 if the problem was addressed in 3.5? Which PixRacer do you have because there was a hardware change to address this?

Thanks for the feedback. From reading the accounts of the Spektrum/Pixracer bug that got fixed in 3.5.1, it was a problem that was created only in 3.5.0 by some changed DMA settings. So, if that is true, that bug would not have affected the earlier 3.4.6. I could be misinterpreting the various comments on the thread I linked to in my previous message, however.
The Pixracer I am using is R14, the latest hardware rev.