I actually removed these thumbnails via CSS using the following block:
.entry .image-wrapper {
display: none;
}
Our site is pretty simple, but this doesn't seem to cause any major issues ¯\_(ツ)_/¯ ymmv!
Did you fix this, @StraydogJW or @Tostado, and could you share how? I have (and want) thumbnails on my navigation page, but do not want them in the blog post itself. Thanks!