I recently seem to be having the same problem with my guinea pig, in the last week he has been chewing and i am sure eating the newspaper that i put in his corners that he uses for the toilet.
He kicks a lot so seems to find the paper when he kicks the woodshavings, I thought the ink is really bad for them although all our papers are old.
would plain paper do any harm to them if they eat it, as just thinking because of no ink.
I have changed him today and sellotaped the paper down so we cant kick it up with the woodsahving and find it or pull it up and chew it, so faw he has not found and is more intrested in his tube which she is destroying the paper off which is safe, will have to buy another on one soon.
anything else i can try and is newspaper harmful to them