Need your thoughts on nose up / pitching down continuesly after capturing the glideslope

Hi guys,

Till P3Dv2.5 I was able to use the Ifly Cockpit Builders Edition and enjoyed it a lot.
As the Ifly CBE does not work in P3Dv3 and it will take quiet a while ,if ever ,before F1 will make it compatible I switched to using Project Magenta ( their 737-800 package : airfile and aircraft.cfg included + FSX 737-800 ), which I owned since 2003.

After several flights I found that the aircraft was too fast on descent and using the spoilers did not slow it down.
As I know a bit about adjusting the flightdynamics I increased the spoilers drag a bit so with full spoilers and throttles to idle the aircraft would slowly decrease speed ( -2200-2500 ft VS ).

My issue is after having captured the glideslope and using Autoland.
Eg:
- cdu refspeed is 132 at Flaps 30
- in mcp 137
- CMD is on
- Flaps 30
- Gear is down
- Speedbrake Armed
- pass load 2/3 full
- fuel total 7000 lbs
- landing weight 120.900 lbs

The aircraft slows down from 160 to 150 following the GS.
Then the nose goes down a bit , the throttles move forward and the aircraft increases speed till 165.
Immediately the nose pitches up , the throttles move bavkwards and the aircraft slows down till 150-155.
This behaviour repeats itself till touchdown, which is way to rough .

Surely I can disengage the AT and mske a manual landing. Then I am able to slow down till 135 and make a nice landing.

I am need to know for sure if I am doing something wrong or not .
If I am causing this I would like to know.

If it is not me I have to start digging in the airfiles again.
Using the complete default 737-800 I do not have this isdue, but its flightdynamics are very unrealistic.

I tried contacting PM several times, but no reply...

Vid :  https://youtu.be/z9L3nMQQ_FQ