Hi Toymaker, (NOT wanting to teach those that already know...) the couplings suggested by Bluejets are intended for angular misalignment, not axial displacement. Of course, the best machines have closely aligned shafts, the cheaper machines often need to be set to a better alignment. Couplings of whatever design will have manufacturers' limits on what axial lateral displacement or angular displacement they can accommodate. The failed elastomer-cross design - in my opinion - may have failed in a "normal" life-time for the ageing and number of cycles, but the failure mode I am fairly sure is a fatigue failure from the combination of age, stress, and number of cycles. If you have used the machine for just a few hours a month then age and stress dominate. That is life. But if you have used it for 40 hours a week for 7 years then you have exceeded the guaranteed life so replace like with like.
Your epoxy repair I reckon will be transmitting higher loads (higher than intended!) To the shaft bearings so those will fail rapidly with continued use of your epoxy coupling. So I recommend you replace with the correct coupling ASAP.
Just my ideas....