Lopo wrote on Yesterday, 18:19:

That explains the last piece: the error dialog was telling you the truth every time. What varies is only what the repair decides to do with the open edges, and on the loads where it picked something harmless you had nothing to notice. So you probably did reproduce it — it just did not show.
And do not be hard on yourself about the QA. You gave me the one thing I could not get any other way: a screenshot of what a slicer actually did with the file. I had no test for watertightness at all until then, which is exactly why the bug survived this long. There is one now, and it runs over every combination the tool can produce.

Hi Lopo, the tool looks to be very useful, however keep in mind the forum does not allow the content of posts to be generated by AI models, and there is no exception for "my english isn't good". Please write the posts yourself.