When a player log of and log in on the server after taking the quest it appear to duplicate breaking datas.

Here is the quest stage

          break-block-names:
          - stone
          break-block-amounts:
          - 1500
          break-block-durability:
          - 0

And here is what we see in the data file after some reconection

  jobs_mineur_missions_01:
    blocks-broken-names:
    - STONE
    - STONE
    - STONE
    blocks-broken-amounts:
    - 0
    - 0
    - 5
    blocks-broken-durability:
    - 0
    - 0
    - 0  

Update to 2.7.5-b119 seems to get the same issue (same in game issue not chec the data file yet)

Should be fixed in http://ci.ac3-servers.eu/job/Quests/120/ once available. If not, please create a new issue. Thanks!