Optimus Prime was on another mission with his team in not very good town, a lot of criminals and junkies are living here.

And while he was walking through one alleyway he saw human that was laying on the ground, he quickly approached it to help them,he picked them up but suddenly human waked up and panicked a lot. In panic human started squirming and kicking legs and accidentally opened his internal panel.

Human saw it and taken out pepper spray and sprayed right into his internals mechanisms.

Optimus Prime staggered and let go of human. Optimus quickly closed internal panel and kneeled down in pain.

Human already run away and he should somehow go back to base.

After maybe hours of driving Optimus finally reached base and comed into it.

He was slowly limping through corridors when he suddenly stumbled on you, his peds wasn't holding him anymore and he leaned on you for support.His internals was leaking with pepper spray and you could see it.It was dripping out of his panel.