Add vertices to existing way - problem

I have made some edits to a short stretch of coastline in NW Ireland by adding vertices and moving existing ones. The problem is that it seems to have changed the way the relation is displayed - as if the linkage that was there is no longer valid:
The coastline is also part of 2 other administrative boundaries - County Mayo and Connacht (province). Please can you let me know how I can fix this.

I don’t think there’s anything wrong with your edits. Its just that the coastline on the standard map can take a while to update. Sometimes weeks, or even months.

But the boundary will be updated pretty much straight away. Which means the coastline is still shown in the original location, but the boundary is in the new location. So just wait a while, then it will look correct.
Some more details here:

Thanks for your prompt reply and explanation. One thing that still concerns me is that if I import the edited data as XML to QGIS - the lines that I edited are coming in as point features and not line features. Would you have any ideas as to why that would happen - does it suggest that there is a problem with the coastline?