TM Mp5Sd6 Strange sound / low power

[macmachine]

Hello,

Today I decided to take out of the closet my TM mp5, the problem is she has been sitting in there for 3-4 years... I got her in 2004, test fired it and got overwhelmed by school work, se she stayed in the closet till today. I picked her, charged my old battery, with no luck: DEAD. I then picked up a 9,6V 2000 Mah nunchuck battery, charged it and got ready to test fire her again.

Here is where the problems started

1- the gun shoot fine sometime, but out of 4 bbs, 2 drop at 3 feet in front of the gun... (hop-up problem?) I fired at a JosLouis cardbox from 15 feets. only 1 bb managed to make a "small" dent in the box... Other ricocheted all around. Back in 2004, I remember shooting my shed by accident, and it magaged to pierce a hole in the plastic covering.

2- when I fire the gun, it make a really hard "clack" sound after each shots in semi as if someting was slamming inside. (battery too powerful?) In full auto, It feed randomly and make anormal sounds.

3- After firing a couple of shots, the gun was smelling as if the motor was overheating, so I stopped shooting immedialy to avoid damage. (battery too powerful again? Or just some dust inside that made the motor smell like that?)

Any thought on what can be done / upgraded to get my gun back to a normal working order? I'm not yet confident enough to open the gun, but if needed, I will do.

Thanks
Mac

excuse the poor english / lack of precise terms, it's not my native language