These are Section errors and are most likely caused by a dirty fiber or unacceptable light level on the receive of the wave interface taking the errors. There are a wide range of other issues that could be causing CVs (CVs cause the ESs to increment) but 9 times out of 10 it is a cable or light level issue. Clean the fibers starting at the Rx port on the card reporting the erros and work your way cleaning every connector in between to the Tx port at the Head end of the Optical Link (the next upstream transponder card) checking power levels along the way and looking for bends in the cabling. If you have any intermediary xWDM equipment, ignore all but those potrs and fibers that connect from the coupler/filter mods to the transponders themselves.
The reason you do not see the errors on the Transparent interface side of the circuit is two fold... First, Section errors are not passed to downtream equipment. The B1 byte (which is responsible for Section Performance Monitoring Capabilities) is terminated at each transponder and then a new B1 is generated for the next optical segment in the link and in the case of the tranparent interface side (facing the customer) B1s are generally not sent or received as this would defeat the whole purpose of providing a protocol independent circuit to them. Second, any errors you did receive on the transparent Interface side of the card would be coming from the customers Tx (the opposite direction).
