Maximoacuello

After getting a few things done to my maxima. Transmission sensor, Break flush and breather hose replaced. Now the abs and tcs off light flashes/ blinks randomly, in one instant even the battery light flashed for a moment. I took it to my mechanic and he says that If it doesn’t happen when he is driving the car, there’s nothing he can do. Earlier this year I replaced the alternator and battery. What do you guys think it can be ?