I recently found about 100 rounds of my BP loads in 45-70 and 40-65.  I believe they were at least 17 years old.  They had been stored in a gun safe in a Montana garage, where temperature swings were high between summer and winter.

I shot them at targets and found that my group size was was quite a bit larger than what I used to shoot with the same loads.  I suspect the lube had gone a bit iffy.   

The 40's were less accurate than the 45's.  The 40 cal shot about an 11 inch group at 200 yards and the 45's were just over 8 inches.   

When fresh, both these loads would shoot less than a 5 inch groups at that distance.

In my younger days I was shooting German surplus BP 11mm ammo loaded in 1888. At 75 years old it was still shooting fine. I reloaded the brass many times and think I still have it somewhere.

Last sunday i shot some 8x58RD that was arsenal loaded in 1931. No hang fires, no duds but some scrubbing at the end due to corrosive primers.
When i was in the army in '85 they said shelflife of rifle ammo was 50yrs.

From my experience, BP will not go bad if stored well, and will still burn if store poorly.  As a child I lived near a military base that had been abandoned in 1893.  I hung out there all the time, and once in a while would find a live round.  When pulled apart, a match would set off the BP from the 45-70's.  So nearly 100 years in the ground was not enough to ruin the powder

My first reaction; 
I'd look at the Peanut Oil container and see if one of the ingredients is Salt. Getting harder to find any food items that the makers don't pour a bunch of salt into "for flavor".
Don't know what LubeGuard is, so I couldn't say if that might be it.
Lanolin and Beeswax should be good to go unless contaminated with something that ought not be there.

This brass corrosion from lube has been brought up before..I have experienced it in my loads..sometimes as soon as 1 year.  My lube is pure beeswax, synthetic spermaceti wax (Charlie Dell), and castor oil.  I think it may be the anh. lanolin absorbing moisture from the air?  These were all smokeless loads.

Most oils/fats will oxidize given enough time. 
Finely refined Sperm oil is a rare exception.  It was highly prized because it was able to hold it's lubricating qualities over very long periods and maintain a constant viscosity over a wide range of temperatures.  It was used for navigational chronometers and scientific and astronomical instruments.

Almost all natural waxes fats and oils will slowly react with the copper in brass creating a waxy green product of corrosion called verdigris.
It is real common to see on antique leather goods where the oxidised fats and residual tanning products used in the production of leather and its preservative coatings will react with brass rivets, buckles, and old cartridges long-time stored in belt cartridge loops. 
I'd not be surprised to see that over time, the fats and oils in a lube could react with a case, a lead bullet, or even powder (if it got hot enough to migrate down into the powder charge).