Dont use wd40 or any of those kero basedthings in an air tool use automatic transmission fluid or buy air tool oil. the symptomyou speak of is typical of ther neoprene o/ring becoming hard and breaking up .my best advice is to take it to an airtool servic centre strange this is the second one of these in 5 minutes

The trigger is sticking internally. Hold the trigger down and give the impact a liberal dose of WD-40 down the air hole, then hook the air line back up after 1 hour.

Best regards, --W/D--