I don't have any experience with this specific problem, but it would seem there are a number of things you could do to help yourself diagnose how to deal with it in your code. First, you don't say if you're using OData 2 or 4 (read-only vs read-write). I'm going to assume you're only reading the data. Your configuration should be readily available for you to review in setup for the field types.
If its working fine in Classic but not in Lightning, that should tell you something about the nature of your problem by collecting some more information on what you're doing differently in Lightning than what you're doing in Classic.
Are you using the Related List Component in Lightning for example as opposed to the related list that's available on the Detail layout? The Detail layout is common between both Classic and Lightning. If you add the related list for this item to your Detail layout on a Lightning Page and don't rely on the Related List Component to display it, does that solve your problem? I strongly suspect it might due to the way the Related List Component is coded in JS as a Lightning Component.
Another thing that might be worth trying is to use the Related Object List component to see if it displays any differently (I wouldn't expect it to, but it might). There's also a free Lightning Component on the App Exchange Called myDynPro that I've been working with that might also do what you're trying to accomplish without needing to write any code. It has a great deal of flexibility and may just do the trick for you.