2006 Pathfinder, 158K miles
For last few weeks ignition key is not getting held in place at ignition switch and can be removed even in ACC or IGN positions, including when driving.
It started as key not firmly held and could move a little bit, then it is not getting held at all.
Transmission shift-lock operation is normal.
Any easy fix other than removing ignition switch assembly and trying to figure it out through complete disassembly?
easiest fix is to ignore it.
Is it causing any issues? Most likely fix is a new key cylinder. In my experience, that’s what has always been the fix in older Fords and Chevys.
I think your only solution is to replace the entire mechanism. Whatever’s worn out inside won’t become unworn by cleaning and reassembling it.
Why not just replace the lock cylinder?
https://www.rockauto.com/en/moreinfo.php?pk=1515766&cc=1433013&jsn=366
Tester
Before doing any of that, get the second key that you don’t use much, or the valet key if equipped, and see if that stays in. A lot of times the key itself wears down to where the cylinder can’t hold it in.
so far I liked @eddo’s “don’t worry, be happy” advise the most 
I have one key on this truck, made no-chip copy and it does not stay put too, so it is definitely the lock, not a key problem (thanks, mr. @shadowfax)
@Tester’s advise is probably the most sound, although $113 is a little bit above what I was willing to spend on it, besides I would get my keys to become different for doors and for the ignition, I would still assume I would need to disassemble everything and transition code pins from my old one to the new one…
I’m toying with an idea to buy something like this eBay used one, then remove the lock cylinder and transition parts.
Thanks for @Tester for pointing how the cylinder mechanics look like, so I can likely remove it with one screw, then figure it out. I’m planning to work on this truck’ timing chain around March-April, probably will remove lock cylinder int the same time and will try to either fix it with what I would have on hands or buy some used unit to scavenge parts.
The key will come out of the locks with the engine running in both my older vehicles. That’s not something I want “fixed”, I prefer it that way. Think of it as a feature, not a problem. For example if I remember I forgot something while leaving from the driveway, I don’t have to turn the engine off. I can just remove the key and go back inside and retrieve what I forgot. Same thing if I want to get inside the trunk for some reason and don’t want to turn the engine off.
If the key falls out and onto the floor however while you are driving, that could be unsafe. So that’s a consideration too. If you just prefer the key stay in like it did when the car was new, try a spare key that hasn’t been used very much as mentioned above. If that doesn’t do the trick, replace the lock cylinder or the entire ignition switch with a new one. One downside with doing that as you’ll need a separate key to start the car and a different key to open the doors. That problem can probablh be addressed too, by a locksmith. But see how complicated this is getting? Can you adjust your thinking to view this problem as not actually a problem, but a feature? If so, solved.
I’ve been installing remote access + alarm + remote start systems from Omega into [almost all] my cars for ages, so I had that feature of “hey, let me get the key off but have the engine running” as a bonus for as long as I can remember, but still I prefer to have the key as something I know I positively locked the steering wheel and transmission if I have it in my hands… oh, well, I will go that “make yourself one more problem” way