My partner takes care of my mother, but they are vindictive and argue frequently. When I get home from work, I am always put in the middle. How should I handle this?

My partner of 24 years is taking care of my Mother. They are vindictive with verbal words. When I get in from work I am put in the middle. Fortunately Mother can care for herself. She is 94, but has an attitude towards my partner who tries to please her. My partner (Maureen) is kind, but has little patience when mother has excuses for everything she does. They are usually small things, but it stresses my partner. Mother has poor eye sight, and moves slow, obviously at 94. Its sometimes an every night ordeal and I am in the middle trying to help each of them see where they are wrong. Any suggestions and or help.