It looks like this has change might have broken some multipolygons (you can see them in the JOSM validator):

civil parishes
<   -2235928 | Taney
<   -2234306 | Stillorgan

Elsewhere these townlands were no longer valid multipolygons this morning:

<   -4622479 | Rocheshill
<   -4592163 | Ballinclea
<   -2195324 | Mount Merrion
< (55675 rows)
---
> (55672 rows)

and these electoral districts:
<  -12495187 | Stillorgan ED
<  -12491366 | Dundrum ED (1911)

and these Anglican parishes:
<  -10742937 | St. Peter's Parish
<  -10709157 | Stillorgan Parish
<   -8851833 | Stillorgan CofI Parish 1900
<   -8811305 | Taney Parish 1900
