Definately switch to powder because powders contain bleach unlike liquids and don't use bio also has no bleach so use non bio powders

Switch from liquid to powder detergent. I was told the liquids contain animal fats that build up in the machine and gaskets. I use fabric softener and have not had a problem but you may try to cut back on it or cut it out altogether.

Is it a front loader? Do you keep the door to the washer closed? You may need to sanitize the door gasket as well as the drum