Find the error in the following sentence.

Explanation

'They used to be close friends but not anymore' indicates that the sentence is in the past tense hence 'have been' will not be used. 'Had been' would be the correct term here. "Very close friends" correctly describes the relationship between the two people. "Until they quarreled/quarrelled" correctly indicates that their friendship ended due to an argument. "Over a petty issue" correctly identifies the cause of the quarrel.