2003 1500 van popping out of gear

I was driving up a slight grade maybe 45 MPH and 3 times it seemed to pop out of gear, any idea why this would happen there is only 53000 miles on the van.
Also my shifter needs a little joggling to get it into park properly, is this related?

Eddy,
Welcome to Automotive Forums..
with that low of miles, it might just be either under the
dash/column, or under the van itself- the cable's housing
might have just a loose mounting bracket..
worst case scenario, it might be a stretched cable..
but look first, and see if cable's sleeve assembly is moving
anywhere along with the shifting cable itself..
also; where the cable attaches to the shift linkage on the
transmission itself, if possibly the the link and/or bracket has
a retention bolt that might have vibrated loose?

Thank you. I should have also mentioned that I have had the van for 5 years and it never went into park properly since day one of owning it, I have put only 4000 miles on it and it never jumped out of gear until 2 days ago, when it did it I let up on the gas and pushed down again and away I went. I will look over what you recommended and see if any of these issues exist.

usually a trans cable down by the linkage, pushes straight forward, and back.. and this turns into a partial 'arch' on the linkage (which has a ball)and the cable end has a receptacle that pushes and pulls through the gear points..
if the cable is not pushing straight onto your linkage, it could be slightly binding as it passes "R" into "P"ark, which is why it has been like that since day one.. the bracket that holds the cable may just need to be tightened, or aligned.. OR, if your cable has a threaded adjustment nut; it might just need to be tightened..
and most ALL the new ones are plastic, so do not break, or you'll be leaving in "N" with parking brake on..

I was driving up a slight grade maybe 45 MPH and 3 times it seemed to pop out of gear

If it only happens when going up a grade it's likely happening due to a loss of fluid. If the fluid level is correct then there could be an issue with the filter pickup tube O-ring not sealing properly.

i led with shift linkage as Eddy1 mentioned "for 5 yrs not going into park properly"; but alloro is right;
contaminated or low fluid could cause slippage out of gear,
or a worn tranny mount too..