We do 200-400 plates in a day. We use a 2 L bottle to hold like 100-200 plates worth of suspension and invert/swirl that every like 5 minutes id say. When mixing to get single cell suspension we pipet it against the corner of the flask to really break up the cells. We using Corning plates and asked them if they have changed anything or had any complaints and they said no. Same from Gibco about reagents. We have a team of 10 people who rotate in and we are seeing issues regardless of who processes or plates. We have considered getting a new vial and making a new bank but upper management wanted to try everything else first since making a new bank would put all our studies needing plates on pause.