This happens to my colonists so much that what you consider a bug I'd consider normal in Rimworld - I have masses of evidence of it in various VODs on Twitch that I could potentially find if you really wanted. The discrepancy is large enough that I'd ask if you can please clarify what you and the game consider 'critically ill'.
As an additional question, can you please clarify whether the priority numbers 1-4 have no weight other than their numerical value? For example, I use 2 as my highest priority so that 1 is free as an override, but some players in my community mentioned they thought that some skills on 1 like firefighting override things like recreation.
I would be delighted if you'd send me any repro cases of these issues! Savegames would be ideal but even videos are worth looking at.
The numbers are just numbers relative to each other. Firefighting can override recreation at any priority level since it's emergency work.