The Title is not missing in the guitar/piano Part Score.
The Title and Composer fields are missing in certain other Part Scores because those text objects are incorrectly attached to the second bar of the Full Score, when they should be attached to the very first bar (the pickup bar).
If System Text objects are attached to any bar other than the very first bar, then they do not appear in Part Scores that commence with a multirest.
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Sibelius 2024.10/7.5.1/7.1.3/6.2/5.2.5, PhotoScore Ult 2020.1, Windows 10 64-bit 16GB. Desktop, and Microsoft Surface Book.
In the Full Score, look at the 'Vokal Solo' stave. Look at the pickup bar. It contains a Whole Bar rest. Change that to a quarter rest. The 'Vokal Solo' part should now show the pickup bar correctly, and the title should return.
You might also want to select the initial barline and edit Gap Before bar to zero so that 'Bass Trombone' (the longest instrument name) fits inside the page margin.