Speed bag techniques
The problem you describe is very common for a beginner. Certain equipment issues can influence the bags rebound. Some swivels seem to influence the rebound a bit, (not much) and a bag that is warped in shape or out of round can create errant rebounds, but I doubt that is your problem the bag is “constant” going off track. That is a sign of either miss hits or making incorrect contact. You may be hitting the bag in the wrong spot, or you may be hitting it with different angles an mulberry purse d movements to cause it to rebound awkwardly. The bag always reflect what YOU do to it, so I imagine you are hitting it inconsistently.
This height will allow your hands to move in the correct motions and help you “punch from all around the bag”. No matter what size bag you use, adjust the board to try and get the belly at your mouth level so you can use the same swinging motion.
IF you are only going to punch in typical boxing method from the front area only, you could set it a little higher, but I mulberry purse personally don’t like to see the belly of the bag up at peoples forehea mulb mulberry purse erry purse d as many boxers do. That really sets up a poor, inefficient swinging motion.