Before anyone can say anything we would need to know more about the problem/detection, e.g. the file name, the location of the file and the malware name, etc.
Because as has been said unless it is a virus infection (and the information mentioned helps determine that), then a repair of the file isn't possible (for any AV not just avast). If the content is completely malicious then the only repair is effectively removal or quarantine.
A repair as has been said is the removal of the virus element inserted in a legitimate file, it is no different for any AV they will be trying to do the same thing. Some may be more effective, but that doesn't change the fact that it is true virus infections which can attempt to be repaired.