@escherstair thanks. To avoid any optimization issue I would also try to use the xPortIsInsideInterrupt() directly in the rpmsg_env_freertos.c code, replacing the env_in_isr(). May I ask you to try on your side?
I can confirm what @qtprashleigh wrote: setting
configUSE_16_BIT_TICKSto 1 doesn’t “stop working” after 37 hours.
Do I understand it correctly that when configUSE_16_BIT_TICKS is set to 1 the issue is no more observed?