Broken multipolygons in Clonskeagh

I render maps of the UK and Ireland, and have set up warnings when certain mutipolygons break. I got this one 3 days ago:

81d80
<  -15448428 | Miltown No. Two DED 1971
1137c1136
< (1134 rows)
---
> (1133 rows)

What that means is that this relation is no longer a valid multipolygon (you can see it’s now a figure of 8). Normally I’d just fix these, but the scale of the breakage near Clonskeagh is enough that it’s probably worth thinking about the best way to handle these.

There are a lot of relations in total here - this bit of river is part of 102 and this bit 94. Not all are broken, just mostly the ones for which this is the north-east corner. Moving this node the other side of the bridge would fix the “north east corner” relations but break any “north west corner” ones.

Fixing it is complicated because many of the relations have the same name:

Some of the duplicate names like here and here seem to have similar tags but different geography, though others like here and here do have different dates. Sometimes the geography varies between dates - compare here with here and here.

I suspect that the work required here might take considerably longer - it might be worth thinking about what the best way of recording some of these relations actually is.

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Ce sujet de discussion accompagne la publication sur https://community.openstreetmap.org/t/broken-multipolygons-in-clonskeagh/111221