I'm not totally familiar with the Titan. We're using a 532-LS, which is similar. Clocking can be a real PITA in a network.
The first thing I would check would be the timing source on the DS-3's. Check the muxes to see if they are both the same.
From there, I would check the timing in the Titan on the DS-1's to make sure both circuits are provisioned the same. This may need to be checked on the HSPM cards as well.
