This can be related to cable issues'.
Make sure you ran pure solid copper ethernet cable, and not CCA cable.
No flat ethernet cables.
The RJ45 connections could need to be recrimped, and make certain they are done properly to 568b standard.
Use Dielectric grease in the Rj45 connection on the camera to prevent corrosion.
You might try a contact cleaner such as Deoxit on the RJ45 connections.