[Qgis-user] problem with modification of vertex

[Andrea Giudiceandrea]

Hi Alessandro,
maybe this is a macOS specific issue. I suggest you to try if the issue 
still occurs also using a new QGIS user profile [1] and with a new layer 
in a new project. If not, then the issue is very likely due to some 
plugin/configuration setting in your current QGIS user profile or due to 
a particular layer or a particular layer CRS or project CRS.

Best regards.

Andrea

[1] 
https://docs.qgis.org/3.22/en/docs/user_manual/introduction/qgis_configuration.html#working-with-user-profiles