Polygons consisting of several long lines are not always filled properly

[yaugenka]

See an example screenshot attached below.
It is taken from this place
http://www.openstreetmap.org/edit#map=16/53.1133/30.1565
and is about this polygon
http://www.openstreetmap.org/relation/7745393

The issue is not constanct. It happens only sometimes with one and the same object.
I have not managed to figure out the exact steps yet but decided to submit it case this can be understood from the code.
The only thing which I noticed it happens quite often after submitting edits.

[bhousel]

Yep, this is #1201. iD can't render multipolygons correctly if they are only partially downloaded. Fully downloading them might take a while, but might be something reasonable to do in a background task.

Most multipolygons are small, but it's the outliers with thousands of member ways that make this issue scary.