For durable glue joints on a platform that frequently hits the ground hard, you need a flexible glue. Hard glues like super glue (CA) or epoxy will not hold.
To fix or reinforce frames, Welder Adhesive or Shoe Goo work great, because the bond to plastic and stay flexible.
To glue camera mounts to FCs, adhesive silicone and high-strength wall-mounting tape are good options. The best wall mounting tape type (independent of branding) seems to be clear, usually with a red peel-off backing. Adhesive silicone can from an even stronger bond than tape, and it also forms a more flexible cushion for the camera to sit on, which reduces vibrations and crash force.