Unlike many threads where the OP disappears, he's posted again more
than once, but for some I don't think specifically addressed this
specific question:

On Mon, 27 Jun 2016 23:41:26 -0700 (PDT), whit3rd
wrote:

On Saturday, June 25, 2016 at 9:09:28 PM UTC-7, wrote:
wrote:

His first post tells us that it only when scanning or copying, later posts

Doesn't the word "only" mean it doens't happen when printing from a
computer.

indicate (nearly but slightly unclearly) that it does not happen when printing
from a computer. That makes it a scanner engine problem, and rollers don't
cause scanner quality issues (only feed isues).

True. One (outlier) possibility is that the scan movement is handled by a geartrain
that has gotten slopppy. More likely, the scan head has a fluorescent lamp which
has begun to get dim and flicker. Lamp replacement is usually possible, but
not always supported by manufacturer repair parts stocks.