I bought the kit with the stirrer last May and I've only used it a few times. I tried to use it yesterday and the stirrer would only "shimmy." I could give the test tube a twist and sometimes it would start the "+" shaped magnet spinning. I assumed the batteries I had were bad so I replaced them with new name brand batteries. This did not change the issues. The kit has been kept indoors in a closet in my house since the last time I used it. I emailed the company but I thought I'd ask here to see if there was some trick to fixing this.