Question: My RF Explorer shows "Pre-calibrating" on screen with firmware v1.11 or newer. Is this an issue?
Answer: Your unit is ok and does not need any external calibration.
That display is expected, it is an info message you will see anytime the unit changes the frequency center or span as it has to internally recalculate many things and recalibrate internal VCOs. For instance if you go to the FREQUENCY MENU and select a new center frequency, the unit will shortly display a "Pre-calibrating" message before the first realtime measurement can take place.
This message was not visible in earlier versions such as v1.10 because these versions didn't support wide band configuration (such as 600MHz span), and therefore the pre-calibration done was too fast to need any user message in all cases. With 300 and 600MHz span introduced in v1.11, it can take a couple of seconds to complete what otherwise may look like a frozen, blank screen if the unit displayed no progress message.
Regardless you see the message (v1.11) or not (v1.10 or earlier) the time it takes for the unit to recalibrate the VCOs after a new frequency selection is the same, the firmware v1.11 just makes it explicit with a message.