I expected this honestly. I had it before. I do not know what causes it. I hope you will find the solution by enabling the “REISUB”. More details at my thread Restarting -> stop job for user running!
I do not know what really caused it, it happened randomly, but recently I am not having it frequently. I was (if I remember correctly) using Grub, but I do not know if it is related or not.
Please let me know how it goes.
If you need any help do not hesitate to ask.
I hope this helps.