Not sure if this one is a bug or is the intended behaviour.

https://mabinogi.nexon.net/news/78002/next-new-beast-update: "The conditions for acquiring the Master title for each skill have been reduced.
* Skills that are rank 1 or higher will only require 100% training experience for the master title to be awarded for that skill."

(Incidentally, thank you for this change. There were so many mastery titles that I had completely given up on which I will now revisit.)

Prior to the update, there were two places you could check whether you had the mastery title. You could open the Character Info window, click on the title box and scroll through the list of titles, or you could open the Skill window, click on the relevant skill, and if you had obtained the mastery title this would be shown below the training count section. I tend to use the 2nd way because it has better usability. The 1st way is difficult because the "Title" window is too narrow, meaning most titles get truncated making them hard to read. The Master titles are particularly hard to read since most of them start "the Master of ..." which means we only get to read 3 or 4 characters of the 4th word, which is the first word that tells us what the title is for.

I now have several skills that are in the following situation.

Prior to the update the skill was at rank 1, it had more than 100 points of training, but it had not obtained mastery. Now, if I look at the skill window for one of these skills, all my training counts have reset to zero, but the progress bar shows that I have completed more than 100 points of training, so it has kept all the training points I had accumulated prior to the update.

For these skills, If I go to the character window and look at titles, I can verify that I have correctly been awarded the relevant Master title, so that part is working as expected. But in the skill info for Weaving, it is not displaying the text to indicate that I have achieved Mastery of that skill.

I don't know whether most players are like me and check whether they have a skill mastery by looking in the relevant skill window. If that is the case, you might be about to receive many many complaints from players who think they haven't been awarded a mastery title they deserve, because they didn't think to check in the titles window, where they would have found that the they do actually have the mastery title.