It's unclear what this deficiency is or if the vaad's claims are true. Nonetheless, the pashkvil (public announcement) is being circulated now in Brooklyn, more than five months after it was issued.
A loose translation made by the source who sent this to me:
Committee to Perserve the Bris
We the undersigned rabanim of Vaad Mishmeres Habris verified that there is to the Mohel Mr. Nesnanel Gross a serious deficiency in connection to his position as a mohel.
We met with him and after a discussion we gave him a ruling going forward.
To our regret Mr. Gross has refused to accept our ruling and has continued performing circumcisions like before.
Therefore we are announcing that it is forbidden for him to continue to perform as a mohel. Until he returns before us and accepts our ruling.
For this we undersigned on Rosh Chodesh Kislev 5775