All errata threads on Firing Squad I found were about specific items, so here is a general errata thread.
Pg. 103, Ballestra
The function of this Martial Art Technique is to reduce the cost of the Edge Action: Shank by 1.
However, in the CRB City Edition: Seattle (pg. 48), the Edge cost of Shank is 1.
Since the cost of an Edge Action can never be zero, Ballestra does nothing.