Help needed - suddenly getting 'bad or no terrain data'

For some reason I’m now getting the ‘Bad or no terrain data’ error when planning a terrain following mission. Terrain following enabled in parameters in mission planner. See screenshot.

When connected to my laptop in Mission Planner it’s not showing any altitude which it always did and the terrain data remains pending and doesn’t load. The Pixhawk main light is flashing yellow, not going green (outside so no GPS issue).

The GPS module green light is on, and the blue light flashing.

I have formatted and changed SD cards and even swapped in my other Pixhawk but no change. This just suddenly started.

I think there is something wrong with the firmware because I also get this even for SITL simulations. It happens at the beginning of boot up for a few seconds then disappears. Perhaps it is a latency issue between the terrain check and terrain upload phases of the algorithm. If this is the issue the check could include a conditional to hold off the no terrain message if the terrain data is in transmission to the RAM…