Large white squares in P3D v4.3

Dear all,

I have large white squares when flying over oceanic airspace. I did not have this issue before in P3D v4.2... Any ideas what may be causing it? 

Here are some links to images:

https://imgur.com/Ut3fyV4

https://imgur.com/zx0D7TJ

I thought that running the FTX Vector Airport Elevation Corrections would solve the issue. I did that but large squares still appear. 

Thanks a lot in advance.

Kind regards,
Marco