If it goes on fine some of the time, then it's likely just the barrel not sitting properly in the slide. I have the same config and it did it to me once, but then I realized the barrel wasn't properly seated. Sure is nice to swap 9mm to 22lr so quickly.

 

+1..I had the exact same problem swapping slides on my 226.

Turns out you may need to push/ put some pressure on the .22 barrel as you seat the slide and rotate the take-down lever.

It probably is a barrel seating issue and looks like it gets easier as it wears in.

Please "push" on the front barrel as you rotate the lever and see if it helps.

Report back with pictures!

 

+1+1
With very new P226, when the lever freezes, I press down the top of the 22LR slide and the lever rotates. This happens maybe 30% of the time. Otherwise, no issues whatsoever.

 

Thanks for the input, but,,,

Not a matter of being able to rotate the the take down lever (although that has occurred as well), when this happens the slide assembly won't travel past the action, just barely engages the hammer in its travel.

 

.22LR conversion

My 220 works fine if I point the barrel up.

 

Sometimes I have to jiggle the takedown lever to get mine on but it is smooth as silk otherwise.