Your bag is crooked. See if you can turn the bag on the emptor so that that the back seam is in line with the middle of the back of the emptor. The "squeal" you are referring to is nothing to worry about. It's just the sound of the armature coming to a complete stop and is actually a healthy sound! If you want to increase the suction of the machine, remove the bag from the emptor. Turn it inside out and vacuum it with another machine. This will clean it very well. It will unclog the pores and the bag will actually feel thinner when you put it back on. It will not get as hard since it can now breathe which will allow for greater airflow!
I actually kind of like the look of the crooked bag.... gives it a lot of character! I will, however, clean it out one of these days. I have heard from a fellow collector that it is a HUGE pain to remove the bag, as the spring that holds it on is extremely heavy.
Well, I managed to turn the bag around to the proper position relative to the Sani-Emptor.... now it looks more like a proper Kirby, lol. It kinda looked like a Royal with the bag on sideways!