The issue you mentioned only affects tickets you’re forwarding.
Please provide the original eml or a bigger screenshot that shows the image being intact.
Also, what your screen is showing is not a removed, but a broken image.
For whatever reason.
Please note that we cannot help you with changed source code installations, because the issue might be caused by your code change. If you provide your eml, I will gladly test the import on a vanilla instance on my end.