That sounds like a fault, probably in the alignment, it should be fixeable if they weren't always like that. With good bins you should always be able to use both eyes, after all that's the point. I got a (backup) set of the Lidl's cheapies and have exactly the same problem with them as you describe. My Bushnell's, Natureview, at about £130 new, are in a completely different league. Having looked through some more expensive ones again I can see the attraction of paying hundreds for them since they are another step up again.
I can see the attraction of monoculars in terms of volume/weight, but I find that a good pair of bins adds so much more to being outdoors, and are essential for bird watching, or mammals at dusk, that I consider them an essential bit of kit.
I just did a quick google and found a great deal on natureview's
here 8x42's for £89.95 and 10x42's for £99.95. No link with the company, except I have bought from them before.