[BScout]

This is about peripherals connected to the HDX card.

Has absolutely nothing to do with Eucon, control surfaces, etc.

What hardware interfaces are connected to your HDX cards?

What you are describing is what happens when the attached interface does not match the sample rate of the session you are about to open. There's a temporary moment when Pro Tools (via the HDX card) sends an instruction to the interface to change sample rates to agree with the session. For that brief moment, the interface appears not connected to the HDX card and then it re-attaches.

When you hit open the second time, the interface is now at the right sample rate so it doesn't detach since it doesn't have to change.

However these things are dependent on what hardware interface you are using. The Avid MTRX does this glitch (because it is really a DAD made interface.) The rest of the Avid branded interfaces I haven't seen do this glitch. I've seen other non-Avid interfaces do this glitch too (Apogee for one.)

There are workarounds/ways to solve this depending on interface.