I wonder why would you _not_ calibrate your compass? That's one of the leading causes of squirrely behavior and crashes, so is leaving the IMU uncalibrated if it's required, which it may be after a crash. Either is easy to do, just follow the prompts in GO or Fly. If the IMU won't calibrate, it's likely whacked and you'll wish you'd bought a Care Refresh policy.
If it's the vision sensors that need calibration, run the Assistant on a PC or big notebook and set the screen resolution so that the test pattern fills the screen from edge to edge. Running it on a higher definition monitor so the pattern is small and centered in the screen doesn't work.
I hope you get your drone flying around Sri Lanka soon...