diff --git a/EKF/ekf_helper.cpp b/EKF/ekf_helper.cpp
index d8c485fb9d..3fd8a3b84e 100644
--- a/EKF/ekf_helper.cpp
+++ b/EKF/ekf_helper.cpp
@@ -566,7 +566,6 @@ bool Ekf::resetMagHeading(const Vector3f &mag_init, bool increase_yaw_var, bool
 
 		// Set the yaw angle to zero and calculate the rotation matrix from body to earth frame
 		euler321(2) = 0.0f;
-		Dcmf R_to_earth(euler321);
 
 		// calculate the observed yaw angle
 		if (_control_status.flags.ev_yaw) {
@@ -576,6 +575,7 @@ bool Ekf::resetMagHeading(const Vector3f &mag_init, bool increase_yaw_var, bool
 			euler321(2) = atan2f(R_to_earth_ev(1, 0), R_to_earth_ev(0, 0));
 
 		} else if (_params.mag_fusion_type <= MAG_FUSE_TYPE_3D) {
+			const Dcmf R_to_earth(euler321);
 			// rotate the magnetometer measurements into earth frame using a zero yaw angle
 			const Vector3f mag_earth_pred = R_to_earth * mag_init;
 			// the angle of the projection onto the horizontal gives the yaw angle
@@ -690,14 +690,12 @@ bool Ekf::resetMagHeading(const Vector3f &mag_init, bool increase_yaw_var, bool
 
 	// update quaternion states
 	_state.quat_nominal = quat_after_reset;
+	_R_to_earth = Dcmf(_state.quat_nominal);
 	uncorrelateQuatStates();
 
 	// record the state change
 	_state_reset_status.quat_change = q_error;
 
-	// update transformation matrix from body to world frame using the current estimate
-	_R_to_earth = Dcmf(_state.quat_nominal);
-
 	// reset the rotation from the EV to EKF frame of reference if it is being used
 	if ((_params.fusion_mode & MASK_ROTATE_EV) && !_control_status.flags.ev_yaw) {
 		resetExtVisRotMat();
@@ -1641,9 +1639,7 @@ void Ekf::calcExtVisRotMat()
 	// convert to a delta angle and apply a spike and low pass filter
 	AxisAnglef rot_vec(q_error);
 
-	float rot_vec_norm = rot_vec.norm();
-
-	if (rot_vec_norm > 1e-6f) {
+	if (rot_vec.norm() > 1e-6f) {
 
 		// apply an input limiter to protect from spikes
 		const Vector3f _input_delta_vec = rot_vec - _ev_rot_vec_filt;
diff --git a/EKF/estimator_interface.cpp b/EKF/estimator_interface.cpp
index 01f6acc9a3..6a580f78d6 100644
--- a/EKF/estimator_interface.cpp
+++ b/EKF/estimator_interface.cpp
@@ -367,24 +367,22 @@ void EstimatorInterface::setOpticalFlowData(uint64_t time_usec, flow_message *fl
 		// check if enough integration time and fail if integration time is less than 50%
 		// of min arrival interval because too much data is being lost
 		float delta_time = 1e-6f * (float)flow->dt; // in seconds
-		float delta_time_min = 5e-7f * (float)_min_obs_interval_us;
+		float delta_time_min = 0.5f * 1e-6f * (float)_min_obs_interval_us;
 		bool delta_time_good = delta_time >= delta_time_min;
 
-		if (!delta_time_good) {
+		bool flow_magnitude_good = true;
+
+		if (delta_time_good) {
+			// check magnitude is within sensor limits
+			// use this to prevent use of a saturated flow sensor
+			// when there are other aiding sources available
+			const float flow_rate_magnitude = flow->flowdata.norm() / delta_time;
+			flow_magnitude_good = (flow_rate_magnitude <= _flow_max_rate);
+		} else {
 			// protect against overflow caused by division with very small delta_time
 			delta_time = delta_time_min;
 		}
 
-
-		// check magnitude is within sensor limits
-		// use this to prevent use of a saturated flow sensor when there are other aiding sources available
-		float flow_rate_magnitude;
-		bool flow_magnitude_good = true;
-		if (delta_time_good) {
-			flow_rate_magnitude = flow->flowdata.norm() / delta_time;
-			flow_magnitude_good = (flow_rate_magnitude <= _flow_max_rate);
-		}
-
 		const bool relying_on_flow = !_control_status.flags.gps && !_control_status.flags.ev_pos && !_control_status.flags.ev_vel;
 
 		const bool flow_quality_good = (flow->quality >= _params.flow_qual_min);