Jeff,
You write that you run the 64-bit OS compiled by JJ on the sBitx v3.
If the sBitx v3 is original, without modifications, then the RPi4 has a total of 2GB of memory. So the 64-bit OS also runs at its limit, and you are also running another program that requires more memory.
If you want to use this, you have to go back to the 32-bit OS.
If you want to stay with 64-bit, you have to replace the RPi with a 4GB or 8GB version.
My 64-bit OS runs on a 4GB RPi4 and I use jtdx and cqrlog programs together with sbitx with an external hdmi monitor. You can check which programs are running and how much memory they require with the htop command entered in the terminal.
You write that you have 21 GB of space on the sd card. This is not the same as memory space.
(if you have such a long error message, put it in an attachment so that it does not take up the useful area of the reader.)
That's it.
--
Gyula HA3HZ
HA3HZ