Images have black outlines appearing on them?

After looking around the site for a while, I’ve seen issues with multiple thumbnails and group emblems made by my friend, myself and some people I’ve never met. It seems that there are black outlines around random images, as it does not happen to all, just a small percent.

This should be completely white around the image, not black lines at the top and bottom

Again, except now on the edges as well

Certain images on the feed page have thick black outlines around them, where it is supposed to be transparent.

This is what the previous image looks like on the groups page, and what it actually should look like normally.

This seems to have been a very recent problem, I remember this beginning to happen 1-2 days ago when I uploaded an emblem for my group and there were black lines around it, I initially ignored it thinking it was a one-time bug

Edit: Here are links to the places with the thumbnail issues, and the group with the image issueᴮᴱᵀᴬ-Bounty-Not-Public-place?id=181049535

Are these all the same file type?

All are .PNG

I’m guessing that without transparency this wouldn’t be an issue then – Would be nice if this was fixed.

A suggestion I made on the Skype group was to add a custom alpha mask where the transparent parts are black.