Thank you for the report. Your report has been highlighted, and we are looking into it.
I encountered this issue as well, today for the first time. The Executor's ability that enables the mass Breach reads "The first time allies inflict Target Lock 20 times on enemies, dispel Breach Immunity and Chaff from all enemies, then each active enemy, enemies who are called in from Reinforcements, or summoned, are inflicted with Breach and Target Lock. These effects can't be dispelled, evaded, or resisted, and last until the end of the battle." This leads me to believe that the issue is not intended and is hence a bug, since the enemy Slave 1 is not being inflicted with Breach, which, in turn, disables you from using your Slave 1's Seismic Charge immediately.
My concern is that the latest patch notes claims to have "fixed a bug where Executor breach immunity is not applying correctly to all types of breach". This leads me to fear that it may be a nerf to Executor rather than a bug. Also, I have had in my pictures issues where an existing ship that does not have breach immunity is not inflicted with breach. The Slave 1 had reinforced before I hit contract.
I agree with the fear, but if it was an interaction with Breach Immunity, wouldn't the target lock also not apply since the reinforcements have Chaff?
Had the same problem for the TB battle in P6 Kessel today:
As you can see my IG-2000 also has no breach lock, only target lock, because he got into battle after the enemy Executor had it's payout
Enemy ships also didn't have it, preventing my Slave 1 to use Seismic Charge as it came into battle despite already having my payout
