Computing shadows should fix the white issue, but if your settings are not on 'very nice' the dirt wil appear very dark.
At least thats my experience with this issue.

Fixed! Computing shadows wasn't it. I only had to change Shader quality from 'Nice' to 'Very Nice'. So thanks for the indirect tip!

spoiler my part xd

people could download your part all this time anyway

Eternity submitted his part, and I made some adjustments so it's a bit more fluid, now up on GDrive.

In the process of finishing up Part04

Fitting 20+ more builder will be intresting, so I started re-using stuff and placing the end of my part more or less next to where I started with just about the same speed. We are at c. 1:47.xxx btw and I really like the track so far

btw can I build the final / very last part?

AX.Unity says:
btw can I build the final / very last part?

I expect the last few parts to be more difficult to work with because of a lack of space, and I have no idea when the last few parts will happen, but if you're OK with waiting until then that should be fine.
Here is the Discord link to the MX FS subchannel where a lot of the smaller discussion happens: https://discord.gg/5rvPNXz

As posted on discord, I have submitted part 5 and Osaka is up next.

someone else should test it then.