Dr1v3n , are you actually sitting in the saddle when riding on the trails? To me at least, your description of riding over a "rain gutter" sounds like you were bucked when the rear wheel hit the end of the feature. An easy skill to practice is to lower the saddle a cm or so for moderate trails so you can keep your butt off the saddle while in an efficient pedaling position. Just hovering over the saddle allows the bike to move under you without throwing you off balance.