I have been experiencing this issue with previous versions of ArcGIS Pro since I started using it earlier this year. It seems that there is a possibility that the application crashes whenever I interact with the symbology of a layer. I have consistently kept my application up to date, and the problem has persisted through all versions that I've used so far (3.2.X onwards).
Since updating to 3.4, the problem seems to have become much more consistent. I haven't been able to edit my symbology without a crash today.