Diagnosis
Yeah, this one's common. The drain hose has a high loop that's probably missing or installed incorrectly, which can let sink water backflow into the machine. The other usual suspect is food debris clogging the filter assembly or the drain pump impeller.
How to Fix It
Start with the simple stuff. Remove the lower rack and take out the filter assembly (twist and lift). Clean all the parts—the main filter, fine filter, and the plastic cup—under running water. Check the area in the sump where the filter sits for any chunks. While you're there, reach a finger into the drain opening (power off!) and feel for any obstruction in the impeller.
If That Didn't Work
The drain hose routing is critical. It must have a high loop (secured to the underside of the countertop or the side of the sink cabinet) that rises above the level of the drain connection in the sink disposal or drain pipe. If it doesn't, siphonage will keep it from draining fully. Re-secure the hose to create that high loop.
Heads Up
Never run a cycle with the filter out or incorrectly seated. It lets food debris straight into the pump and can kill it. Also, avoid using those solid detergent pods if you have persistent drainage issues; they can leave a gel-like residue that gums up the works.