"Field Elevation set 0" messge in navigation with optitirack

Dear all,

I am experimenting with Copter navigation using Optitrack.

Copter-4.3.7 maybe 4.3.8 is also navigating without problems.

However, when I try with 4.4 or higher, I get the message “Filed Elevation set 0”.

Does this affect the flight?
What can I do about it?

Thank you.