Is there any phrase that figuratively yet succinctly captures the meaning of 'going back to do something difficult that has been done in the past yet has never been resolved'?
For example, imagine a never-ending debate over some political issue. The two sides have temporarily decided to put the issue on hold but eventually go back at it again (although there is hardly any hope for resolution).
'Going back to fight an old war' (that I mention in the title) seems to be one way to say this.
'Going back to the old trenches' seems to be another.
But I am wondering whether there is an even simpler and perhaps commonly used way to express this in literature/ writing?
Edit: Clarified that I am looking for a figurative expression and I added an example of a situation that would satisfy the expression.