Hello @PTESandro and welcome to the forum 
Thank you for reporting this. For checking apparent bugs, a report should be made against the latest formal release which is version 5.3.4.
So, I’ve tested this on Linux with the 5.3.4 appimage and also a recent 6.1.0-prealpha (development branch) appimage.
The bug as you describe it is still there so I’ve changed the category (and tags) of your topic to be Develop: Artists Feedback &Testing, to get the attention of developers.
You’ve described the exact situation in which you found the bug.
The full situation involves the Text Tool, the Edit Shapes Tool, the Calligraphy tool and the Comic Panel Editing Tool.
(The Select Shapes Tool is not affected, probably because it’s not a ‘creation’ tool.)
Among the four tool that are affected (they are ‘creation’ tools) the individual behaviour is slightly different in different situations and gets messy to desribe.
The strange thing is that this behaviour happens with a layer that is a copy of another vector layer but does not happen on a vector layer that is not a copy.
When I have time, I’ll try to make a full analysis and description but I hope a developer can look at this in the near future.
In the meantime, can you please make a formal bug report at https://bugs.kde.org/enter_bug.cgi?product=krita (Sign up and login are needed.)
Then post a link to the completed bug report in a reply in this topic.