Cleavage plan is usually not a issue when cutting Oregon Sunstone. It depends on the crystal growth it self. As in other rough crystal you may find a hard surface, which makes you think your lap is not cutting, as well as a soft spot sometimes.
I have worked with a lot of Oregon Sunstone rough over the years and the soft spot is caused by soft end grain of the growth plates in the crystal. It is like trying to polish the end of a board, end grain. Try a soft touch and be patient as it will take longer as you may be going against the grain and it is trying to feather. If that does not work try reversing your lap so you go with the grain, remember a soft touch here also so you don’t jam your stone, done that not fun.
I have had good luck with Jon Rolf’s Greenway. That is all I have used on Oregon Sunstone for a couple of years now. It will move your meet points and leave a polish at the same time. I cut with a 600 to a broke in 1,500, then straight to the Greenway for meet point and polish. Make sure to break in the lap.
Hope this helps