[issue] clicking error when labeling 3D image data

[callmebigbig]

hi, thanks for your amazing work on this convenient plugin.
I want to use it to label some structures of knee in 3D MR images. There is no problem in handling single or very few images. However, when I import the normal series images and follow the routine, the first click will be ok, but the following click will lead to the sudden enlargement of image numbers and the labeling won't work anymore. It will be great if you figure it out. Thanks!