DIAGNOSIS That's a drain issue. Either the drain hose is kinked/plugged, the drain pump is weak, or there's a high loop problem letting sink water backflow into the machine.
FIX First, check the most common cause: the drain hose under your sink. Make sure it's not kinked and that it's installed with a high loop (the hose should rise up to just under the countertop before descending to the drain or disposal). This prevents siphoning. Also, check your kitchen sink drain/garbage disposal for a clog.
IF THAT DIDN'T WORK The drain pump might be partially clogged or failing. You'll need to disconnect power, remove the lower kick plate, and check the pump for debris. Sometimes food particles get past the filter and jam the impeller, preventing a complete drain.
HEADS UP That standing water will start to smell bad fast. If you've checked everything and the pump seems to run but is weak, the pump itself is likely failing and needs replacement before it quits entirely and floods your kitchen.