I’ve replaced the ProJET TCM 310 LAN EnOcean LAN Gateway with a Symcon EnOcean LAN Gateway and repositioned both the EnOcean Gateway and EnOcean Repeater (Eltako FSRP-230V) around the premises. This has resolved the issue with the ‚EnOcean Gateway (KeepAlive): Waiting for response timed out‘ warning.