Deposits on magsafe connector board - should I worry?

Just received a 2nd hand 2015 Macbook Pro 11,5. It's from a reputable dealer with many shops and good guarantee service - wouldn't have bought in absence of that.

I quickly and carefully opened the case to have a peek and check all is OK. The system is working fine on a trivial, initial power on & boot test. What I see on the magsafe connector is as pictured (click to see detail of deposits on connector board):

I have not detected any other issues yet except for a loose small object rattling in the upper right case (possibly a lost case screw).

Questions:

(1) What has likely happened to the magsafe board?

(2) Will this impact reliability?

(3) Will replacing the magsafe board achieve anything? (I see it's available for $40)

Thank you!