How does the pneumatic tube station work?

I mean, I get the basics of how a pneumatic tube system works. But I was recently accused of causing the system to go down because of sending a tube when there were too many incoming tubes that hadn't been cleared. I don't think this was my fault since I took my empty tube from the pile of arrived tubes before sending, but it made me realize that I don't know the finer points of the tube station, I just put my tube in the sender and hit "lab".

Are there any tips or tricks to troubleshooting the tube station? Are there things to watch out for that could accidentally cause a traffic jam in the tubes? Is there a weight limit, like if I have to send a bunch of stuff on ice and the tube is basically packed full of sample bags full of ice, will that overload it somehow? Has anyone had any weird experiences with their pneumatic tube system?