First. I'm very happy to find this forum.
Second, I see that I'm not the only one to have this problem
2-3weeks ago, the right front door window fall down. I found that the cable was attached to the regulator inside a kind of sleeve (made in plastic

)
I call my dealer and the replacement part cost $177.00 can. Why this is so expensive. This is because you also receive the motor, the cable, the protectice cable tubing. You cannot only get the regulator itself.
You known what, today,the front door window just fall off with the exact plastic break sound. At the moment I'm typing that reply, I have not check inside of the door but I'm sure this is the regulator. The motor still working well, I ear the cable going back and forth when 'playing' with the window switch.
Should I told you that I haven't try the rear windows.
For me, this is a design problem. This is not normal that so many peoples have this problem and not only on the Jeep Cherokee.
So far, it seem that I will need to buy two complete system.
If someone have another suggestion how to fix it, please let's express yourself
Thanks