I bought the $100 Ryobi scroll saw from home depot last month and have not really done anything with it until today. I was practising on an old 1/4" piece of plywood. It started doing this thing where it makes a weird sound like a horse exhaling through its lips and it seems as though the blade speeds up for a second at a time. It seems to do it randomly every 10 to 30 seconds or so. I've searched the internet for a good half-hour now and cant find any info on this issue or if its even a problem. Can anyone give me some advice on this? I'm still really new to this and am not sure what could be causing it. Thanks