The upgrade to 12.1 was successful, and I really like the new theme with the butterfly.
I ran into some trouble with the SD card after the upgrade: it told me the card was corrupt and needed to be set up before using it. I backed up the data and let the phone re-format the card (to use as portable storage, not internal). Afterwards, I ejected the card, mounted it on my laptop and copied the data back over. Upon re-inserting it in the Volla, it again told me the SD card was corrupt. I re-formatted it again, but instead of ejecting the card to copy the data, I plugged the phone into my laptop and transferred it via USB. It worked for about 30 minutes, and then again told me the SD card needed to be re-formatted.
I again ejected the SD card and mounted it on my Linux laptop. The file structure seemed fine, but I re-formatted as ext4 instead of the Volla default of FAT32. This seemed to correct the issue, and I was again listening to podcasts stored on the SD card, but after about 20 minutes of listening, the audio stopped, and I saw the phone once again said the SD card was corrupt and needed to be set up again before using it.
I made sure to set the same owner and group Volla used when I would save files to the SD card for the copied-over files and folders. I also set the permissions on files consistent with Volla's behaviour.
Has anyone else had problems of this sort?