In some aspects, the disclosure is directed to methods and systems for monitoring and isolating issues over physical layer (layer 1) paths using Flexible Ethernet (FlexE) protocols via client-based operations, administration, and maintenance (OAM) management. Each node within a FlexE communications path may dynamically insert, extract, and/or replace OAM messages from FlexE data streams as needed to ensure that the OAM messages may be provided unimpeded to a destination (e.g. monitoring server or other device), as well as inserting additional monitoring data (e.g. bit error rates, delay measurements, loss measurements, threshold crossing alerts, or other such monitoring notifications or data) for intermediary nodes.