It has been my experience that many musicians and especially students focus on the wrong things when sight-reading a piece of music. The main focus for many, whether intentional or not, is hitting the right notes. But from a purely technical standpoint there is another aspect of the music which is significantly more important than note accuracy and that is the rhythms. If I could choose to sight-read a piece of music with a musician who either plays all of the right pitches or nails all of the rhythms I would choose the latter every single time. A player who sight-reads with great groove and rhythmic confidence will make everyone around them feel more confident.
When I have a student who struggles with groove when sight-reading, whether stopping repeatedly or adding/taking away beats, I have them try something which almost always works. I have them read the exact same etude a second time and play the entire piece on a middle F. Invariably a player who couldn't get past the second line without stopping can sight-read the entire piece down with almost perfect rhythm and groove. This proves that the player was too focused on playing the right notes and not enough on the groove.
Never sacrifice the groove of a piece for note accuracy even when sight-reading.