It means that the Threshold is set too high and MegaDrum thinks that the edge switch is always pressed. Lower Edge Threshold one notch at a time until you get reliably only bow notes when you hit the bow.
Or it means that either the cymbal or the cable is broken and there is a short on the edge input between the sleeve and the ring.
I raised the gain to 8 and lowered the threshold and got it to correctly trigger edge and bow notes. The threshold is very low though, at 2. And I don't get why I suddenly had to change the parameters, I'd been playing the hh for more than a year without issues with my old settings. I hope it's not the sign that something broke in the cymbal.
When the edge switch is not pressed, there should be infinite resistance between the sleeve and the ring. When the edge switch is pressed, there should be close to zero Ohm resistance between the sleeve and the ring if it is a dual piezo/switch cymbal or close around 10 kOhm if it is a 3way Yamaha style cymbal.
I did that and it behaves as you describe, so hopefully the cymbal is ok after all.
Thanks !