At around 08:30 UTC we went in TCS room where the power supply is located, and also looking at its analog display, we saw that it was delivering intermittently, as indicated by the LSC_WI_HB_moni signal.
We replaced the power supply with a spare one of the same kind (Kert 420). During the replacement (from 08:34 to 08:40 UTC) the operator temporarily opened the WI etalon loop, as recommended by Maddalena.
Now the loop seems working regularly (attached fig).
