I was getting "[lpe] mocap timeout" messages all the time
What I did to fix that was to re-stamp every message received from Vicon (in my case) before forwarding those to PX4 (using mavros)
msg is of type "geometry_msgs.msg.TransformStamped"
Then I re-stamped every message using the time of the companion PC (Odroid, Raspberry, etc..)
msg_nwu.header.stamp = rospy.Time.now()