While we had enabled power saving for the vivante gpu on the #librem5 since some time we couldn't power off the corresponding regulator (power supply) since the phone would hang then. Turns out we just didn't give it enough time to come back up. Fix is already merged into linux-next: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=3b66e4a8e58a85af3212c7117d7a29c9ef6679a2
