The fault symptoms you describe appear to have more to do with the media than the player.
The player seems to be working fine most of the time but the jumping fault is variable - it comes and goes. The CD disks you play are variable.
When it next jumps put the disk to one side and play it several times over. Make a note of where the jump happens. Examine the playing surface.
Good luck...
Peccavi
May 2013