FX Impact m3 leak from mystery spot ?

Got a leak from the add on 2nd reg gauge , I believe I got it from Huma but not sure the manufacturer . It is the little oval hole where the pencil points to . I’ve looked at schematics and still can’t find the source . I’ve already replaced the oval shaped O-ring behind the gauge plate between where it attaches to the rifle frame .
Anybody had this one go bad before - you might save me a lot of searching .

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Got a leak from the add on 2nd reg gauge , I believe I got it from Huma but not sure the manufacturer . It is the little oval hole where the pencil points to . I’ve looked at schematics and still can’t find the source . I’ve already replaced the oval shaped O-ring behind the gauge plate between where it attaches to the rifle frame .
Anybody had this one go bad before - you might save me a lot of searching .

View attachment 575551
Yes, there is an o-ring that goes in the oblong opening, should have come with the kit