Intervals.icu complaining for data recording interval

Maybe is related to GPS setting? 
I will check on my intervals.icu account 

not intervals but did not see any notification about 4 sec recording 

Fair point. 

I have different sources in Intervals.icu (Garmin Connect, Strava,...). This might be related to from where the data is downloaded.

Update: I've tidied up connections in Intervals.icu to get activities only from Garmin Connect. Will see on my next training. Also will check on my PC original fit file if this really missing accuracy.

I seem to recall, most Garmin units will force 1sec recording when there is a power meter connected, I wonder if this is a unexpected 'feature' that needs fixing when there isn't a power meter connected but setting = 1sec, not Smart ? 

You need to see the actual fit file data to see if the garmin is actually not recording 1x per second (I'm sure it is). Then see where intervals.icu is getting the files. Best bet would be to have Garmin Connect feed intervals.icu

I checked the FIT file with no power meter connected and the unit set to 1 second recoding and it was recording every 1 second.

If you wish to share the FIT file I can check it.