static bool prev_use_old_behavior = true;
bool use_old_behavior = _manual_control_sp.aux1 < 0.3f;
if (use_old_behavior != prev_use_old_behavior) {
  PX4_WARN("using old behavior: %i", (int)use_old_behavior);
		prev_use_old_behavior = use_old_behavior;
}
if (use_old_behavior) {
  ...
} else {
  ...
}