My dad just got his horton TR 175 with red dot scope. At 20 yrds you can split hairs with this thing but at 30 things start to get somewhat shaky as far as accuracy.

Horton puts that dial on the side where you can click up the scope to achieve better accuracy at a distance. Sometimes it hits real good at 30yrds, other times we seem to shoot low or it pulls off the right. Its just not hitting as precise as i would like. I was told the string can throw off the bolt if it is locked somewhat off balance...is this true? How can i correct this?

Also, I have the Horton red dot scope on this thing. Shot great the 1st day. Yesterday the internals fogged up and you couldnt see through the thing. Any advice?