That's a common issue, in my experience. Lots of folks used to play them open bottomed, and/or not case them. Draw a perfect circle 13" in diameter on a piece of paper. Take the heads off yours and lay it down over the circle. Trace when it doesn't match it in a different color - and mark, on the drum shell, where it's out of round. Label each such location on the drum and the paper. Remove the drum from the paper and measure the distances between the perfect circle and the differently colored areas; that'll tell you how much the drum is out of round. You may be able to squeeze or malletize (use a towel around shell) back to within 1/8' or so of being round; if so, it should tune. I tried this on a replacement 9x13 that exhibited the same symptoms as yours; it was 1/4" out of round. After this treatment, it tunes well and sounds great.

That's a common issue, in my experience. Lots of folks used to play them open bottomed, and/or not case them. Draw a perfect circle 13" in diameter on a piece of paper. Take the heads off yours and lay it down over the circle. Trace when it doesn't match it in a different color - and mark, on the drum shell, where it's out of round. Label each such location on the drum and the paper. Remove the drum from the paper and measure the distances between the perfect circle and the differently colored areas; that'll tell you how much the drum is out of round. You may be able to squeeze or malletize (use a towel around shell) back to within 1/8' or so of being round; if so, it should tune. I tried this on a replacement 9x13 that exhibited the same symptoms as yours; it was 1/4" out of round. After this treatment, it tunes well and sounds great.