If the related products' images are being cut off (as in, they're too tall for the container), you can add this snippet to increase their height.
Try adding this to the bottom of customise.css.
Go to Themes > Template Editor > under Assets, open customise.css, and add this at the bottom:
height: 250px !important;
min-height: 350px !important;
You can modify the "250px and 350px" to be higher if needed, just makes sure you keep the increments the same. (E.g. if you change the first one from 250 to 300 (50px increase), be sure to increase the second one from 350 to 400px, also a 50px increase, to keep them consistent).
That's all to it.