Washing machine dirtying clothes?

Maintenance

I've a tenant who has contacted me saying that despite repeatedly cleaning (branded and bicarb/vinegar) the washing machine, her white washes come out grubby and the machine smells.
I've asked and she confirms the door and drawer are left open. I can't prove otherwise. Shes pushing me to get a new washer. I feel I can't just take her word and replace what is a perfectly good machine, nor do I want to go around for 2 hours to check before and after a wash.
What would be recommended course of action