Hello,

Before splitting a way, as you did for this one (https://www.openstreetmap.org/way/1150973353), it is always a good idea to download the entire set of elements around it, including its relations.

In this changeset, you split a part of the roundabout but the relations using it were apparently not in your active JOSM layer.  That creates a gap in all those relations—several bus routes and local cycle routes—because they are untouched and refer to the only object they know, which is only one part of the roundabout.

Don’t worry, it’s all fixed.  I thought you might be interested to know about this kind of issue. 