Hello,
To give you some backgrounds, I am working in railway signalling engineering... and I could keep noticing some (minor) inconsistencies in the ETCS system.
First, "Entering FS" or "Entering OS" messages should be displayed only during level transitions when the speed limits and gradients are not known by the onboard system for the whole length of the train.
So you should encounter that message only when entering an ETCS domain, not in the middle of it.
Also, while it's usual to have this message when entering level 1 from level NTC (National Train Control, such as SHP), it's much less frequent to have this message when entering level 2 (from level 1 or NTC) because, usually, the RBC knows the speed limits and gradients before the level transition and transmits that information to the train.
For a transition from level 2 to level 1, you shouldn't have this message either because the speed limits and gradients from the RBC are kept by the train during this transition.
Also, according to the DMI specification, when the safe radio connection indicator appears, you should not have the Sinfo sound triggered.