Prevent polygons from overlapping after splitting them in QGIS


I have a FileGDB with several polygons. When I split them using the Split Features-Tool, they overlap with other polygons within the same layer I did not split.

Here are some screenshots:


Split: the two blue circulated polygons were split. Red are the errors topology checker shows:

Only merging some polygons using the merge selected features tool doesn’t create an error/overlap:

Doing the same thing with the same data but in a .gpkg also creates overlaps after splitting the features.
same thing in .gpkg

I'm using QGIS 3.36.2 (but the same problem already appeared in previous versions). The CRS is EPSG:2056 - CH1903+ / LV95.
Topology editing is off. It does not make any difference whether I select Allow Overlap or Avoid Overlap on Active Layer.

Does anyone know, how I can prevent polygons from overlapping after splitting (and/or merging) them?
Some sample Data can be downloaded here google drive link.

Best Answer

You need to enable the "Topological editing" feature available in the Snapping toolbar

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