What other possible reasons could there be for having scored rotors ? This has been happening to my front left disc since I replaced the rotors + pads with Stazi's Ti pads about 15k km's ago.

What led me to notice it again was the squealing noise I'm getting when braking.

Braking performance seems fine, unless I've been missing out since replacing them.

Could improper installation of the pads cause this ?

Thanks.