Sooner or later I have this error in dmesg on RPi 4B 4GB RAM. I have plenty of RAM free all the time.
I see this error occured when there was 3.2 GB free RAM.
Maybe upstream will have this fixed in the next kernel. I have linux 5.4.75-1 compiled and ready to push but it requires upgraded bluetooth firmware which we have but we are trying to test every scenario we can with bluetooth using 2 different .service files with devices we each have. Hopefully I can get the new kernel and bluetooth related packages pushed to the unstable branch tomorrow.