Brush is definately challenging sometimes....

I think it's because limbs just don't give enough flat reflective surface for the sound pulse to bounce off of...

Can you give us the following:

(Is this 455kHz or 800kHz...??)
(What chart speed is this..??)
(Did you mark the waypoint as soon as the brush went overboard or did you mark it by re-passing over the brush...??)

Rickie