Another question about our little Red's constipation.

[Wally]

Our Buddy is still constipated but was able to pass the stool on his own tonight. It was the size of a pea ( Ouch) I noticed a dry lump right at the start of the stool that I believe was acting like a plug or cork, same as last night when I had to massage it out of him. I've noticed that he's chewing, and as far as I can tell, eating a lot of wood and that it may be wood fiber blocking him. That makes me wonder if his digestive system is irritated by something or that he's missing something in his diet.
I haven't changed his diet at all so I'm stumped.
The wood he's eating is some kind of pine branches that he's basically ignored for the three months they've been in there and the untreated pine his cage is made of.
Any ideas?
Thanks, Wally