I suspect it's Zeefaring items, or closer to that? On account with no Zeefaring, no Zeefaring items, 167 Persuasive the difficulty is 54%, but add one Zeefaring item (<a rel="nofollow" class="external free" href="https://fallenlondon.wiki/wiki/M._D_%27_A_for_:_F_Edition">https://fallenlondon.wiki/wiki/M._D_%27_A_for_:_F_Edition</a>) and it went to 84% chance.