Thanks for the feedback. I run on Fedora and do not use suspend-then-hibernate, so unfortunately I cannot test it.
I also can’t find any information for this error message (besides your reddit post)
Maybe (I am very new to systemd and D-Bus myself, so this is just a guess) it helps to register frameworkd as a systemd service.
I you know how to get around with the configuration files, there is already a first draft for a systemd service file.
You also need to change the dbus service (/usr/share/d-bus1/system-services/org.stefanhoelzl.frameworkd.service see systemd activation)
With systemd-inhibit --list you can also chech who tries to inhibit certain logind operations.