Weapon Mastery challenge/achievement bug

[SulfuradoG]

There are achievements called [weapontype] Mastery that are obtained after leveling X number of weapons of a certain weapon type to level 10,20 and 30. They are bugged. 

I only noticed this bug a while ago, with my cronus (because until then i hadn't read the challenge description). It is the only sword that i have, and when i hit level 20 with it, I noticed the progress on the blade mastery II challenge, which is having 5 swords over level 20. But then when i leveled it up to 21, it counted again, and again until level 24, where it had counted the same sword five times for the achievement, each time it leveled up. I went back to the achievements, and noticed it had happened with every weapontype that i had. 

This isn't a gamebreaking bug, but i felt like making a bit of noise about it nonetheless.

[popsyWobbly]

I also ran into this recently with a single Bow, Blade, Pistol, Sentinel and Shuriken.