If you don’t hit 60 degrees at least once every couple of weeks and use liquids you will always get a build up of slime, gunge, algae inside your machine. Like the vast majority of machines on the market yours has a totally sealed outer drum so you can’t get in to physically clean it.
No dedicated maintenance wash as such, you just use the hottest setting without clothes and a small amount of green box powder every few months.
I moderate on a trade forum,
www.ukwhitegoods.co.uk. If you go to the help section at the top of the home page and look for appliance care and cleaning there is plenty of good advice from people who have had fifty years or more experience.
Look up ‘smelly washers’
Jim