Current TW on Lenovo T450s, legacy boot, no UEFI. /home is encrypted (LUKS).
RAM 8BG, Swap 4 GB in /dev/sda1. Kernel-parameter: resume=/dev/sda1
splash=verbose quiet showopts plymouth.enable=0 . 

Resume from hibernated system leads to reboot, I'll elaborate:

I send the system into hibernate via KDE-button. Screens wents black, flickers,
mouse reappears, it takes some time (around a minute) and then the computers is
off. No problem so far. I close the lid.

I open the lid, computer boots, behaves as if resuming. When resuming worked,
there was a little flicker just before the graphical screen asking for my
password appeared. But now, the computer reaches this point, but then just
reboots.

This was an issue since monthes, hibernate was not stable. But now, since a
week, it doesn't work at all. s2ram is stable.

I've seen this bug: https://bugzilla.opensuse.org/show_bug.cgi?id=842285 .
However, we are on a current TW with dracut.

I'd be happy to provide more information, but please consider I'm a user, not
an expert. Thank you!