ffmpeg gif frames overlapping when made from transparent images

Question

I'm trying to make a gif from a series of transparent pngs but when I play the resulting gif back the frames overlap the first frame can be seen through. Here's the command I was using(as part of a larger program I'm working on)

ffmpeg -framerate 7 -i "B:\\documents\\Visual Studio\\Projects\\WindowsFormsApp1\\bin\\Debug\\tmp\\%d.bmp" -lavfi palettegen=stats_mode=diff:max_colors=256:reserve_transparent=1[pal],[0:v][pal]paletteuse=new=1:dither=none:alpha_threshold=128 -loop 0 "B:\\Pictures\\Gif frames dump\\output.gif" -y

but more simplified

ffmpeg -framerate 7 -i image%d.png -lavfi palettegen[pal],[0:v][pal]paletteuse output.gif

Here are the frames that got overlapped and here are the input images

Edit: I tried on this the nightly(ffmpeg version N-93851-gdcc999819d), 4.1.3, 4.1.1 and 4.0 windows 64 static builds. All had the same result. I've gotten the same result from simply trying to convert an apng to gif.

Only the first frame sticks around if stats mode is "full", or "diff"; however, every frame stayed onscreen when set to "single". So I'd definitely say there is something funky going on with the disposal method