Ouch! Miroslav and PoolMUC have identified a stinker of a bug in the monitoring. As you can see from the .csv PoolMUC points to:
ts_epoch,ts,offset,step,score,monitor_id,monitor_name,leap,error
1723614741,2024-08-14 05:52:21,,1,19.00510025,24,recentmedian,,
1723614741,2024-08-14 05:52:21,0,1,18.477138519,56,plszy1-361g4fk,,The observed offset should be appearing between 05:52:21 and 1.
There is no offset provided by the server with a zero-payload response, but the monitors are treating that as an impossibly perfect sync resulting in a zero measured offset. Better would be to treat it as if the response showed leap 0b11 (3). It may be desirable to log it with a unique error message to make it distinguishable from an unsync’ed server, but the key point is it should be treated as unusable.
@Ask or other monitor code maintainers please take a look.