Most dishwasher trouble begins in the rinse, not in the motor. The machine still runs, the cycle still finishes, and the glasses come out looking slightly cloudy. That is the moment to start a log, because the cause is usually something you can see and clear yourself.
What goes wrong first
The spray arm holes fill with mineral deposits and food particles, so the water pattern thins out. The filter at the bottom of the tub collects debris and slows the drain. Rinse aid runs low, so the water dries in spots. Water that arrives cooler than the machine expects does not activate detergent well, and the film builds up over several cycles.
Each of these causes shows up in the same places: the glass, the inside of the door, and the bottom of the tub after the cycle ends.
What to log
Keep a short written note for each cycle that looks wrong. Record the load, the detergent used, whether the rinse aid dispenser is full, and what you see on the glass and the tub floor. Note any standing water at the end of the cycle and any new smell. A pattern across several entries tells you more than a single bad load.
Also note how long the cycle takes compared with the cycles you remember. A cycle that keeps getting longer points toward a drain or filter issue.
What you can check yourself
Before you call anyone, cut the power to the dishwasher at its supply. Remove the bottom rack and the filter, rinse them under running water, and scrub the holes in the spray arms with a soft brush. Turn each spray arm by hand; it should spin freely. Check that the drain hose is not kinked and that nothing blocks the air gap, if your model has one.
If the film returns after these steps, or the water still pools, the problem may sit in the pump, the valve, or the wiring. Bring your log to the visit. The written pattern will save time and show the technician where to start. The dishwasher guide on this site gives the planning context for a unit at this stage.