Hello!
This is a very rare problem which only seems to show up when an Intel HD3000 on a Linux system is used. Unfortunately there is no fix yet to solve it.
But if it would be enough for you to remove / hide the trees, I will be happy to provide you with a simple mod that prevents the engine from rendering the trees at a certain camera distance.
Just write me a short email to info (at) train-fever.com and I can send it to you.
Best Regards,
Tom
PS: If you write the mail, German is fine for me too 😉
