I have a black and Decker electric 16" hedge trimmer. It has started making a very loud squealing noise from around the motor area. I have tried taking the blades off, cleaning and oiling everything, I took the casing off hoping to find an obvious answer but didn't see anything. I could not get it to make the noise with the case off, but after a few minutes of use after putting it back together, the noise came right back. When the noise starts, the blade continues moving, but won't cut. Any ideas? Thanks in advance.