a commonly accepted repair is to make plywood gussets. These are simply triangles of 3/4" CDX with a pocket cut out in the apex that fits the ridge board snugly. You apply construction adhesive on the rafters, slide the gussets onto both sides then screw in with deck screws about every 6". Most AHJs will allow this in lieu of collar ties if done on both sides of the rafter. What it does is transfer the loads all along the rafter ends. As long as the triangles are not too small, enough 'meat' of the rafter will handle the tensile loads along the bottom chord and compression load at the top where they oppose one another.

HTH

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