Adding instruments results in invisible parts in mixer and blank information of the instrument

1) Create new score (Ctrl + N)
2) Select any template / choose any instruments
3) Add new instrument through the "Add or remove instruments" panel (I shortcut)
4) Add any instrument to the score and press "OK" button

When adding and instrument and verifying its part properties, I'd expect to see the standard name and range of the instrument, as well as the long and short names commonly used for such instrument; I'd also expect to see the instrument and/or its part in the mixer, in order for me to use VSTs, SFs, etc. in it.

But following the steps previously mentiones, they lead to there being a new stave in the score, but instead of indicating the characteristics of the instrument and part (such as the range of the instrument, the long and short names of the instrument, the clef used to read in the instrument and the part name), there simply appears a number and a stave with treble clef; the range indicated is C -1 to G 9 and although it's possible to see the new part/instrument in the instruments list at the side of the palettes, there is no new instrument appearing in the mixer, meaning there is no sound to any notes written in such stave.

When trying to workaround this bug by replacing the instrument in the part properties, the result is that there appears a null space (as if there was no text there) in all the characteristics of the part and instrument.

OS: Windows 10 Version 2009, Arch.: x86_64, MuseScore version (64-bit): 4.0.0-2620385256, revision: abc123456