Strange problems with autopilot/gps

Have flow several missions with my Skywalker, exploring Ardupilot capabilities and had very strange behaviours today…
my system:
Skywalker 1680
APM2.5.2 running 2.74b firmware
UBEC on input side no jumper…output servos (micros) run by esc bec
Ublox CN-06 GPS with 3DR config

todays mission…three waypoints about a mile or so apart…
first at 1000feet rel alt
second at 2000ft
third back down to 1000ft
rtl atl is 300feet

manual launch and climb to ~300feet
then switched to AUTO…
-first problem is that throttle went to THR_MAX and I shortly [color=#FF0000]lost GPS lock[/color] :astonished: …looking at logs bat voltage its fine…so I have no idea why its loses lock…log shows it does anytime very high throttle occurs…
note that between WP1 and 2 it climbs very gently with throttle only about 50% to gain the same altitude as between home and WP1…evidently throttle management changes from initial WP to interWP ?

-second problem is after reaching WP3(the last one) it starts to descend (it should its in RTL, right? with a 300 foot setpoint)…however I switch to FBWB and instead of holding the alt when the switch was made it continues to dive toward RTL alt until I switch to MAN and then back to FBWB, when it correctly holds the switchpoint’s alt…is this expected behaviour? like FBWB uses RTL’s alt set point until cleared by switching to MAN…sounds like a bug in the code maybe?

any insights to the gps loss, full throttle on WP1 climb vs interWP, and alt setpoint issue when switching to FBWB would be appreciated…Tlog attached…

First, can I ask where your GPS is mounted, and what FPV gear you have on board.
You have a lot of electrical noise associated with your throttle, and your compass is not healthy. Please post a picture of your installation.

FYI a HDOP of less than 2.0 is good, and you really want 9 sats min.