Heltec CubeCell fails to join TTN V3 OTAA in basic station mode

Issue: Join to TTN V3 failing with OTAA & basic station mode

Setup: Heltec CubeCell HTCC-AB01

LoRa® Server: RAK7258, firmware - LoRaGateway_1.2.0065_Release_r209

Setup CubeCell with RAK7258 gateway and registered on TTN V3 as basic station. Gateway shows up on TTN console as “connected”. The gateway system log keeps showing “user.err.basicstation[1525][SYN:ERROR] Repeated excessive clock drifts…” and “user.warn.basicstation[1525][S2E:WARN] ::0 diid=11582 [ant#0] - unable to place frame”

I am using the LoRaWan.ino example from “HelTecAutomation/CubeCell-Arduino”

On TTN console I see “Receive uplink message” for Gateway with the correct devEUI & appEUI. On the end-device I see “Accept join-request” message, but no data

On the Arduino Serial console for the CubeCell I see “-> join failed, join again at 30s later”. Also on the CubeCell I see LED flashing Blue->Yellow-Red