Figure 1. The temperature of the NI etalon control started dropping today. Looking at the monitoring of the heating belt output it became intermitent.
This issue has appeared several times in the past and was solved by replacing the Kert power supply: https://logbook.virgo-gw.eu/virgo/?r=67582
We should consider starting to make the replacement of these power supplies on fixed schedule based on past expererience (for example changing them every year or two) instead of waiting for the power supply to fail and then have a thermal transient in the etalon loop lasting a for several days.