It sounds like there is debris in the sump which isnt being pumped out.
When you remove the filter at the base there should be a metal grate which should life up, which will reveal the void below where water sits.
Please this out with a sponge and try and remove any traces of sand particles, run the washer back on a rinse, and reinspect the void to see if it showing signs of sand.
The black bits may also from a failing component such as the water softener, or heater, so by running it just on a rinse it just circulates the water around, after that then run it again on a high heat \ intensive wash and see if you get the same fault.
Please let me know how you get on.
Hi Mary, I havent heard back from you, do you require any further assistance?
If not appreciate if you can rate the service received, so I may close the case
Hi Mary, just wanted to follow up and see how you got on cleaning out the sump of the dishwasher?
Hi Mary, I havent heard back from you, if you have everything you need, please rate the service received using the star rating, so I can close the case.
Should you need any further assistance please advise how I can assist you further.