F5 looses the token for the first call

Do you have any similar issue? or any idea :

with the token that it has retrieved from the AD Entra ID endpoint. The first call to the backend always loses the token on the way via F5, so it does not reach the backend at all. The frontend then goes to an error page (no authorisation).
If you then start the same call again, i.e. reload the frontend, everything works as expected.