Before this thread bounces more among the usual related topics and instances of failures and proposed fixes, it might be a good idea to take some time to read the early sections of
this post from Deep South Robotics, even though most of the post is about advanced navigation using satellite signals. In the field on some jobs where there is a higher risk of GNSS unlock, I will check the
GPS Plan app on my iPhone to see which satellites could possibly be "seen",
at that time, by any of the receivers on my drones. That app also quickly shows which times of the day are better than others for the maximum number of satellites in view from my location.
More frequently I will check
UAV Forecast before going to a field location (and later on my iPhone with the app) to see the estimated Kp Index value and other forecast conditions. All of that operator prep is to gauge the risk that I may have to switch to non-GNSS ("manual") control in that location after a launch. As hinted in the Deep South post, the constellation of satellites being used in one time period may not be those that are used in the next time period. I have three mRo receivers (and one from Drotek), on masts, with the newer 3DR shield.
Even then there can be an unlock situation, as happened three times on one job while hovering low to the ground in deep woods on a hillside when the Kp Index value was Not Good. A quote attributed to Louis Pasteur: "Fate favors the prepared mind." Some practice and muscle memory on the control sticks helps too. If you don't have that experience yet, in many situations you can raise the throttle stick to go higher and give yourself time to regain your composure and decide what to do next. By that time your Solo may be up high enough to regain lock.