Faulty relay would mean BOTH sides wouldnt work, one working side means its fine!
Unlikely both r/hand bulbs have failed - if one end had come unplugged then you would still have one working albeit flashing a lot faster?? Wouldnt hurt to check them tho, strange things happen when bikes get dropped...
I will run with what Jon is saying and go with feed problems, IE the switch - it canceling the other side when you push it across does not mean you have electricity feed to the new side
Do you have a Haynes or similar for said bike & can identify wires coming from the l/hand handlebar switch?
Swap the feed wires to the l/h and r/h indicators, that would tell you if you have a feed problem.
