hmm...could be the machine is just low on chemistry. After about a week or so, or after any kind of heavy use--the front tanks in the 2150 start to get low. Since the chemistry in them is being circulated by the pump back to the working tanks--you can often hear this sucking, bubbling type sound as the level drops. Eventually it gets louder, and then when it gets low enough, the float switches actually shut the machine down.
My question is how many prints have you made, and when was the last time you changed chemistry? I've made a few hundred prints in the past week on ours, and it's been 7 days since changing chemistry and I can hear this noise right now...it can sound like it's coming from under the machine, but it's really at the bottom of the front tanks.
fwiw---if you open the machine, the levels will rise in the front tanks. To get a good idea of what they actually are--get a small magnet and place it on the sensor under the dryer--to the right of the drive gear on the wash rack. If you get it in the right place, you should be able to run the machine with the lid open. This is always the first thing I do when troubleshooting weird noises in the machine.
It is possible to trick the machine though. You can turn it on and run it for a couple of hours with low chemistry and eventually it will sound a warning beep or a series of beeps, and the warning light will flash on & off. Eventually it just shuts down. You can fool it by switching it off for about 15 minutes or so and then turning it back on. It will warm up for 5 minutes or so and then run for about another hour and then start complaining again....I only know this because of a coworker I once had who was too lazy to change the chemistry out on his shift. He'd always cheat the machine along and wait for the next guy to do it.
Hope this helps--fingers crossed it's just the chemistry level. We did have a pump go out once and it's an expensive part to replace and a PIA to get at as well.