By complete coincidence, last Sunday I happened to do the exact same measurement. It came about because I set up my QO-100 station again and I decided it would be nice to do a 24 hour doppler measurement to check that my receive chain is properly frequency locked. For the test I was using a GPS locked Octagon OTLSO, GPS disciplined Ettus B210 and SDR console 3.0.21. The plot shows the beacon offset for 36 hours starting on 5 April at 1938 UTC. I also thought the wiggles were intriguing. Please keep us updated Daniel!