Weaponmaster 10 AB not working

[Fargreze]

Description
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My character is missing the new 1AB he should be getting from reaching WM 10.

Steps to reproduce
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Level to a total of 13 WM levels on my character.

Expected result
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AB math on this character is...
23BAB + 15 str + 3 WF/EWF + 3 weapon AB + 2 twohanding + 3 WM AB + 1 Epic Prowess = 50AB.

Actual result
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Instead, I come out to only 49AB, both on the character sheet and according to the combat log. This makes me suspect the new +1AB at WM 10 is the culprit. Weapon feats appear to be correctly chosen.

Notes
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Relevant Feats visible on character sheet: Weapon Focus (2H) , Epic Weapon Focus (2H), Epic Prowess, Superior Weapon Focus (from WM 5), Epic Superior Weapon Focus (from WM 13).

[Flower Power]

I wonder if this is potentially because it's a 2H weapon?

2H Weapons on Arelith seem to interact very weirdly with a lot of feats/class powers, especially ones that have Arelith-specific changes: example, they don't get the correct bonus AB from DC's Divine Wrath (they end up getting 2 less than they should, which is why I suspect it has something to do w/the 2H +2 AB bonus.)

[Tarkus the dog]

Same case with my character, at least on PGCC. I'll check on the live server too.