No, let's just leave it up to the DM. If we were to write rules, the checks should happen rarely enough that droids should turn defective in the middle of an adventure.
Yeah, I'd rather not include specific rules.
So, shall I add the amend the Defective Droid as follows and declare it finished?
Defective Guardian Droids
A poorly maintained droid may become defective, causing it to act erratically or even break down. This mostly happens to droids that have been exposed to the weather, since rain or windblown particles eventually wear through the droid's seals and corrode or jam delicate inner workings. Droids that work indoors in stable climate conditions rarely malfunction.
A defective guardian droid has the following changes to its statistics block. Any statistic that is not listed is the same as a normal guardian droid:
Droid, Guardian, Defective
Initiative: -2
Speed: 40 ft. (8 squares)
Armor Class: 16 (-2 competence penalty, +8 natural), touch 8, flat-footed 14
Base Attack/Grapple: +3/+4
Attack: Laser +1 ranged touch (2d6) or slam +4 melee (1d6+1)
Full Attack: Laser +1 ranged touch (2d6) or slam +4 melee (1d6+1)
Space/Reach: 5 ft./5 ft.
Special Attacks: Laser, defective droid
Special Qualities: Construct traits, damage reduction 5/adamantine, defective droid, radarsight, radiospeech, robot traits, tracked chassis
Saves: Fort +1, Ref -1, Will +1
Abilities: Str 12, Dex 10, Con —, Int 10, Wis 11, Cha 1
Skills: Listen +5, Spot +5
Challenge Rating: 3
A defective guardian droid gains the following defective droid traits: