To be able to separate between different artists sharing the same name I have adopted the Discogs naming scheme, adding additional numbers in brackets to an artist's name. This worked fine until the upgrade to v3.1 (3.1.6426)
In the example below I have added a performer credit for "Gavin Dunne (2)" which gets correctly listed in the Peformer column. However, when opening the artist window again the "(2)" gets cut off and parsed to the role field even though the tag is still correctly present according to the tag browser.
When I switch to text display the entry gets (in)correctly displayed as "Gavin Dunne: 2" as well.
This seems to be a display problem only, though. When I add an additional artist to the list Gavin Dunne is saved as "Gavin Dunne (2)" again.
 A bit of further testing showed that this only happens when using the "Performer" credit. When adding an artist as "Guest Artist" for example it will still be listed correctly next time.