Loud noise upon braking

Making a relatively low-energy landing in my DG-300 (s/n 3E1) on
Sunday, I modestly applied the brakes and instantly heard a loud
buzzing (?) noise. I released the brakes, the noise stopped, and I
reapplied the brakes and heard no noise with normal braking power.

This is a TOST drum brake.

A cursory inspection of the main wheel/brake assembly revealed nothing
out of the ordinary -- though the drum appears to be dragging on the
wheel at various points around its turn (*very* softly dragging, i.e.,
not turning friction-free) -- not sure if it was this way before.

Should I investigate this further?

Thanks,

Eric