[2.0.45] Black horizontal line drawn intermittently

[BurninSun]

Video and save file attached. Line is appearing at the chunk boundary just a few tiles south of the starting position.


This game was started with space exploration (and the same graphics glitch existed there) but I've stripped it back down to vanilla and still get the same seam.
The seam only appears while moving south while the player is north of the seam and only at the current saved zoom level (4 zoom out clicks from default).

Edit: Log file added as well.

[BurninSun]

Looks like a mod changed the thread title but I need to clarify - this line appears day and night regardless.

Also there is 1 chunk boundary that always has a line while an adjacent chunk never has a line while the others only appear when I'm moving south.