First waypoint - the drone stops and doesn't proceed with the mission

Check if your cruising speed is not zero.

Sounds like high wind velocity.
At WP1 press the pause button, wait a few seconds then continue the mission.

I never heard of this message, most likely “Actions are disabled with curved turns”

The curve size at WP1 is always zero, a curve can only exist between 2 lines, i.e. 3 points.

It would be helpfull if you shared your mission in the Mission Hub: