Yes.How many types are there?
If a key is broken,what triggered it?
Torn keybed? Bent Keyframe?
What is all that stuff?
What causes it?

I had issues on a key,but wasnt really a key.
Seems like a whole octave.

My "A" starting to acting up,seems like a screw loose or something but still response greatly,no stuck,but once in a while if i hit that key a few randomly times,it sound like a torn paper inside it,and also,same octave,last night,the "E"
was suddenly stuck,could only press it halfway,i didnt force to press it again,then it was all fine again.
But most of the times,both keys was fine.

Should i be worry about this?
I just picked it up from the service centre last week,did a small check on the "outside".

Is it possible when they open it,the keys just seems out of place and things happen?

Working is learning.
Don't play hard,play smart.