Hi @michael.coyner,
It seems we have a few flashing sprites today! (I just read another post with this issue today). This has happened in the past. Here is a post that talks about the “why” and suggests a fix to simply delete sprite and put it back. I did that with your kong sprite (here is my remix). I did have to copy it from the original and paste it into a new sprite but that worked. It is no longer flashing. Also, I believe the trailing with the walking kong had to do with your background. Your original background was very tall with some whitespace at the bottom? Almost as if the canvas was very tall but the image only took up some of that space. (See screenshot below). Anyway, I deleted that background and added it again and the animation no longer trails. It does sound like you have resolved the issue with @wutadam’s fixes.
Have a good day!
~Michelle