79 Series jumps out of first gear

[Brunswick]

My 79 series 2019 single cab 40K on the clock jumps out of first gear when going down hill. It happens on a fairly steep hill when setting off. It has also happened when descending sand dunes. it pops out of first in both hi and low box. Has any one else had experience with this issue. Thanks

 

[Shayne]

My 80 did that a couple of times when i removed and replaced the gearstick , i guess i added a little to much grease but it fixed itself .