The link went to the specific brand new errata posting. It's not in the errata document yet, that's only collected once a year (or with a new printing).
p91, Trenchworks/Fieldworks Engineers (TRN)
"Each turn these infantry units may convert an area under a 2” AoE template into a fortified area."
change to
"If these infantry units stand still during the Movement Phase, they can spend their Combat Phase to begin fortifying an area. They may not attack, spot or take other actions during this Combat Phase. During the End Phase of this turn, place a 2” AoE template in base-to-base contact with the infantry unit's base as the fortified area."