I spent some time this morning on the HAM8-GS13 v1 issue reported here by Jim, causing a 0.6Hz table oscillation. While working on it, the GS13 (or something along the chain) decided to fix itself. The problem has not reappeared -yet- since then.

1- Jim set the ISI to offline @18:21 UTC. We see GS13 v1 ASD x2 below v2 and v3 (fig1)
2- With the ISI offline, I sent a Z excitation and tripped the ISI @ 18:54 UTC.
3- Restarted the Z excitation with smaller amplitude between 18:55 to 18:57 UTC. The x3 vertical GS13 ASD now match (fig2)
4- Turning off the excitation, v1 asd is still matching the other 2 vertical gs13 (fig3)
5- Turning on the loops. No 0.6Hz anymore (fig4) ...

Puzzling... We'll continue to monitor.