Hi,

what is this alert mean ?

That you Time Of Day has changed or is out of sync with incomming LTC.

These airspeeds are hyper sensitive with LTC signal issues and depending or your time distribution scheme the amount LTC and the pc's clock can drift which leads to all kinds of weird warnings and errors 

Thank you for your info , but it is a strange thing that the server time is synced with domain controller time ! is it recommanded to create NTP server instead from sync with server time ?

I would first check the airspeed is correctly reading the incoming ltc.

A simple test I do is to hook up a small audio mixer to hear the ltc timecode and to be able to meassure and change the audio level. It would not be the first to time a LTC (audio) distribution amplifier is not connected correctly or is not handling symmetric/asymmtric levels corectly.

I also download an adroid ltc generator on my android phone

https://play.google.com/store/apps/details?id=com.AaronBernstein.ltctimecodegenerator&hl=en

and hook it up to the same mixer through the minijack headphone output. (I have also used android emulators for Pc but a phone is more practical for a temporary testing setup.)

Now check the behavior of the airspeed while changing levels and ltc source.