I have a similar problem with Amazon links like this:
<iframe src="https://rcm.amazon.com/e/cm?t=tuahufodiguam-20&o=1&p=8&l=as1&asins=0750656948&fc1=000000&IS2=1<1=_blank&lc1=0000FF&bc1=000000&bg1=FFFFFF&f=ifr&nou=1" style="width:120px;height:240px;" scrolling="no" marginwidth="0" marginheight="0" frameborder="0"></iframe>
I’m afraid to open posts with the visual editor to update them as they seem to randomly ‘clean-out’ the embedded amazon links.