I asked the developer. We think the part is in a bad state. This is not a regular error.
If you file a PR we may be able to fix it, but we are not sure at the moment.
Hi, thanks for your answer.
Finally I deleted the sketch and made it again, with no apparent issue. The sketch was working properly though, it was just a lost of reference.
The error came after some heavy deletion of features, not a common operation... Seems everything is ok now after running geometry validation.