"This issue has been hashed over many times but we still have no solution."
Does it mean that the subject was very important and was difficult to agree on? Or is it because they were talking in a meaningless way?
It doesn't even mean the issue was important. You can hash over a celebrity break up as well.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
hash over = hash out = discuss = thoroughly discuss the issue of [the proposal]; careful give consideration to a problem [proposal]; thrash the matter out of
Hasn't the committee finished hashing over the question yet?
We must hash out the question of Mr. Brown's appointment, which many of the directors are opposing ..
We hashed the plan over.
They hashed the question over interminably
Let's hash the main ideas over!
hash over = recapitulate, summarize briefly