Hey again and thanks for the quick reply on the posAtCoords throws "Cannot read properties of undefined (reading 'top')" when content has no client rects issue.
I have found a similar issue however with posAndSideAtCoords method. posAndSideAtCoords is called by basicMouseSelection on every mousedown/mousemove event. When the editor or an ancestor is hidden, detached, or mid-layout at the moment of the click, the same scan crash occurs.
Appreciate the help and effort put into this 