FX .22 caliber Tarantula leak question

My tarantula developed a leak for the air gauge. I fixed that and tried filling after I had cocked the gun.

It is now leaking out of the screw towards the front of the forearm that holds the stock on the receiver????

IS there a reason for this. Supposed to be an oring under the stock screw?

Any help or info would be Greatly appreciated. 

Do not want to send in to get fixed unless I absolutely have to.

Got the gun used years ago from AOA who resealed it before they shipped it to me. 

Who would be a good person to fix the gun for me if it comes to that?

Thank you to all who reply.
 
Part list and service manual attached if you want to fix it yourself - FX2000, FX Tarantula different name, same model

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View attachment FX2000-part list.1649401856.pdf

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View attachment FX2000-servicemanual-original.1649401872.pdf