I’ve found (at least) two systemd warnings:
[ 826.459642] systemd: /usr/lib/systemd/system/plymouth-start.service:15: Unit configured to use KillMode=none. This is unsafe, as it disables systemd's process lifecycle management for the service. Please update your service to use a safer KillMode=, such as 'mixed' or 'control-group'. Support for KillMode=none is deprecated and will eventually be removed. [ 826.480243] systemd: /usr/lib/systemd/system/stop-dmesg.service:2: Unknown key name 'USER' in section 'Unit', ignoring. [ 826.487724] systemd: Configuration file /usr/lib/systemd/system/attach-bluetooth.service is marked executable. Please remove executable permission bits. Proceeding anyway.