In the editor, create a new file, and go to the MA: Advantage tab.
Press the "New (Copy)" button at the bottom left, and find "+1 DV for Unarmed Combat. Remember the position of the one you chose - 1st, 2nd, 3rd, etc. - unfortunately, there are 6 of them, and the Unique Id that's in parentheses after the name is cut off.
Now, press the "Eval Scripts" button on the top right.
Press the "Click to add another eval script" text.
Press the "Find Thing" button. Choose "Martial Arts Advantage" at the top, and then find the item that's in the same position as what you copied. Double-click that one.
You'll see that a string of characters has been added to this script - it'll look like:
maaBoxDV
Select and copy that string of characters, then press the "X" to the right of this second Eval Script, which will delete it - this set of steps was needed to get the Id, but you won't need a second Eval Script.
Press "OK" to leave the Eval Scripts form. Find the "Replaces Thing Id" box on the right-hand side, and paste the copied text there.
Now, at the top, in "Unique Id", add a new Id - using something similar to the original Id will make this easy to recognize as a replacement. For example, maaBoxDV1.
Okay, that gets the housekeeping out of the way. Now for the fix.
Press the "Eval Scripts" button again. This is the line that adds the damage bonus:
Code:
perform hero.child[wpUnarmed].field[wpDamage].modify[+,field[trtFinal].value,"Boxing"]
Here's that line, re-written to cover natural attacks, too (but excluding the attack of will):
Code:
foreach pick in hero from BaseWep where "Equipment.Natural & !thingid.wpAttWill"
perform eachpick.field[wpDamage].modify[+,field[trtFinal].value,"Boxing"]
nexteach
Press "OK" to leave the Eval Scripts, and exit the editor (unfortunately, replacements can't take advantage of the "Test Now!" button for a quick test). In the Develop menu, make sure that "Enable Data File Debugging" is checked, and then choose "Quick Reload Data Files" from that list.
If you can figure out which of those 6 items applies to the martial art your character uses, you'll only need to fix that one, or you can create replacements for all 6.
I've also got your report of this issue that was sent through the bug reporting mechanism, and I'll be adding this issue to my to-do list, so once I get the chance, I'll apply this fix for all of these - at that point, you can delete the fix file you've created.