Mistrust means "to doubt, to lack confidence in". It does not necessarily imply any serious suspicion of malice or bad faith.

This can happen in everyday life in situations where the parties otherwise trust each other, but find themselves questioning that trust. Mistrust is different from distrust

Distrust

Distrust is a formal way of not trusting any one party too much in a situation of grave risk or deep doubt. It is commonly expressed in civics as a division or balance of powers, or in politics as means of validating treaty terms. Systems based on distrust simply divide the responsibility so that...

, which means much the same but adds suspicion to the mix: it is reserved more for a situation where bad faith is suspected.