@slup - what say you my friend?
Mmm ...
The winds was much stronger than what the OP thought ... & also in a direction that easily can be thought of being the reason for the AC reaching the shore in that strange even arc.
We also know that the OP was warned 3 times regarding entering a restricted zone & that he should exit the zone promptly ... the first time 65,8sec, the second time at 153,7sec & a last time at 543,3sec.
If we look at the second time the warning came up ... & look at the stick inputs and the total achieved tilt angel for the AC (a
MA2 shall be able to tilt up to 35 degrees during strong winds).
The yellow hand drawn arrow on the sat picture marks whats covered in the chart further below ... the AC (red star with a green bar telling the yaw direction) is where the second restricted zone warning came up.
And here the same (yellow path) in a chart ... the dotted graphs is the stick commands (value 1024=neutral), the red height, the dark green heading speed & the blue is the total tilt angle. (have placed the marker in the chart at the zone warning 153,7sec.
(Click on it to make it larger)
As seen ... the AC comes in with a tilt angel of very close to 35 degrees with a full forward elevator input against the same strong winds as later in the flight, just there the AC tilt angle suddenly becomes much smaller & the heading speed goes down to mainly a hover without any obvious reason.
This really looks like an invisible wall to me ...
Looking further into the DJI Fly Safe material & comparing that to the zone warnings that came up show this ...
(Click on it to make it larger)
And adding in what DJI say about the BLUE zone ...
This really looks like a problem with the blue zone authorization ... it mainly stopped the AC (possibly by limiting the tilt angle) when not obeying the first warning & depending on the stick inputs the OP made when the AC was in that "arc path" (which mainly was left aileron + forward elevator), the restricted tilt angle ... & adding in the strong wind & direction made the AC take that arc path in towards land.