Aye Simon,
Nasty!

These are the two (2) long through bolts, which pass through the outer crankcase cover and thread into the Right Hand (R/H) Crankcase. If I remember correctly, removing the outer crankcase cover is essential when re-threading these holes in the upper R/H crankcase.
I haven't been able to go a pull and old pair of cases out, but I think that the two holes are blind, so that it might be possible to re-drill the holes and helecoil them, with the engine still on the side stand!

However, you also stand a very good chance of introducing aluminium swarf into the crankcase/ oil, unless you are able to cover the open crank case during the operation.

You also have a fair chance of drilling eccentric holes with a hand held drill and finding the helecoils are not installing squarely or as deeply in the casting, as the bottom of the hole maybe full of swarf!

Also how tight are you tightening these set screws? I'm not suggesting they be slack, but tweaking them up with a 1/2" square drive is not necessary. Something like 10ft/lb is plenty, I think.
Proper job is engine out, strip the cases, drill on a pillar drill and helecoil or else fill with weld and re-drill the holes, then tap to original thread size. Cheap and cheerful, which might work due to low stress, would be to fill the holes with Araldite or American 'Monkey' metal, then drill and tap, as before. Then rebuild the motor. Not what you want to hear, I think.

SteveL, SteveH, Ian650 and Andy230 may have different ideas with this problem on SRX motors and there are plenty others whom may think other action possible. 002 will no doubt have a tried and tested 'Trade' fix. I hope my thoughts don't put you in despair.
My regards, Bill.