Since there is misunderstanding regarding the components of contact cleaners and solvents based in pressurized or non-pressurized cans, I will go into a bit more technical explanation.
First, we need to show an example of application:
WD-40 in action, direct surface sprayed first (with remaining residue not propellent), and then open torched, by "experts".
Next, we need to explain what contact cleaners are:
WD-40 (and other contact cleaners) specifically are hygroscopic (not "hydroscopic") compound meaning "water displacing" solvent, that actually ATTRACTS water to the compound and promotes rust, if not removed, which is common to ALL contact cleaners used with metal surfaces, unless mixed with other chemicals for other use to make the long term effect inert. They "stick" to metal for a reason. This is not a good thing for metal on metal contact parts, whether guns, or pinball assemblies, beyond flammable characteristics.
Next, what compounds make these cleaners:
If people want to read what makes these components dangerous for use in pinball machines:
Read MSDS documents and learn the components of products of use in chemical components, or disagree.
I would look at the other aspects beyond aliphatic hydrocarbons.
In this case, WD-40.
And the final notes:
Many of these same chemicals are found in similar products, or additional chemical chemicals added that are even more combustible.
It is not exclusively the aerosols that make products flammable.
Not all contact cleaners are CRC certified as non-flammable when dry, even today.
Most will not fully evaporate when applied.
My secondary background is chemistry, beyond engineering, in manufacturing.
This is about as simple as I can make it.
If you want to use any type of contact cleaners on pinball machine parts for any reason, the part must be removed from the machine.
After it is cleaned, all residue must be removed by detergent, or a good scrubbing with soap and water.
The parts must be fully dry, before reinstallation.
Lubrication is performed during reassembly with a non-reactive compound oil, non-organic, readily available today.
Preferably, one or two single drops one the end of a pointed solder hand tool before the assembly is placed inside the game.