Advice on Trim [porpoising] not related to PIDs, FLYING wing setup

I have a flying wing and while there probably is a small issue with structural flexing between the fuselage and the high aspect ratio sweep wings looking at the log I wonder if there is a trim issue as well causing porpoising, servos seems to fluctuate a lot. The wing is setup as two elevons RC1,RC2 and two spoilers RC5,RC6.

Here is the log bin file:

Any thoughts