Rockbox playback broken, Fuze+ playback OK. Huh?

Any idea why Rockbox playback suddenly sounds like I’m underwater? And how to fix it? I had a full Fuze+ and added a 32 GB SDHC chip. Moved the files from Win 7 explorer from one to the other. Spot-checked playback and it was fine, so I then removed the files from the internal memory. However, a few days later when I go to play those tracks in Rockbox, it sounds warbly and chirpy, with all manner of odd noises. If I reboot under Fuze+ firmware, these tracks play back fine. I installed a newer version of Rockbox (I had the “latest build” from a few months ago, and updated with the latest build from a day or two back), but no change. I know the player is fine. I know the chip is fine. I know the files are fine. How do I get Rockbox working again?

Here’s some further information… it is partially solved, but not utterly so.

Initially, the warbly playback survived multiple reboots (between the two firmwares), as well as an update install of Rockbox. So I  attempted a complete install of the current build (adding a new Theme while doing so. Afterward, I rebooted the player, and sound playback issues were gone. Wonderful!

Then I changed themes to WoT while the music was playing–instant warble. Still playing, I switched back to the cabbiev2 theme I had been using. Warble gone. Very weird, especially since WoT had never been on my player before! So it appears, after a number of trials, that changing themes during playback can make the Fuze+ player unstable.

I’m okay with that, since I rarely change themes. However, the original problem being able to surviving reboots concerns me, because rebooting the player did not solve it. It took a full reinstall (everything but the bootloader). On this occasion, the warble appeared to be the cause of changing themes, yet rebooting cleared it up. Hopefully that will remain the case.

If not… I’ll be back!

And if anyone has a better understanding of why this may have occurred, or easier solutions, please say so. I’d love to understand the real cause and solution to this odd behavior.