So somewhere before or after the first boss (Price Phalus) magicae becomes completely unusable. I first thought it was the left trigger not being recognised anymore by the game. However, when rebinding it to another button, it still does not work.
Hence in conclusion, magicae is just completely absent for my playthrough, somewhere quickly after being able to use it.

The other two bug reports are not that bad, just a minor inconvenience. However, missing a complete feature, pretty much required to further some Arx dungeons, is very annoying. I am casting the game aside, which is a shame, as the game is actually very lovely and I like the combat system as well.

It is not technically a new issue: https://steamcommunity.com/app/759570/discussions/0/2692512878724307583/
Especially what Spexxy mentioned, since he also has it working at first and breaking somewhere along the way.

Debugging steps:
- This was played with version 1.4.16_3, as seen in the main menu.
- Tried on Ubuntu (Wine), as well as Windows 10. Both have the same issue, so not OS-related.
- Bought a new pc last week, which has the same issue, so it is also not (internal) hardware related.
- I also tried with the keyboard, there it doesn't work as well.
- Rebinding also does not fix it, it is always the magicae button not working.
So hence I am thinking it is not actually an input issue, especially since magicae worked initially.
- Health is 100% on all attempts. Also tried to sleep (in-game), but that does not fix it.
- There is no cue at all (sound or animation), even the log does not show it, even though it shows 'Change magic' or 'Change magic to first' messages for switching spells.
(See below for the relevant log)

This is my save game, since for me it is reproducable with it: Save game.

Log entry. Between every change of spells, a casting was attempted.
---------
Start Character

(Filename: C:\buildslave\unity\build\Runtime/Export/Debug.bindings.h Line: 45)

Change Magic

(Filename: C:\buildslave\unity\build\Runtime/Export/Debug.bindings.h Line: 45)

Change Magic to first one

(Filename: C:\buildslave\unity\build\Runtime/Export/Debug.bindings.h Line: 45)

Change Magic

(Filename: C:\buildslave\unity\build\Runtime/Export/Debug.bindings.h Line: 45)

Change Magic to first one

(Filename: C:\buildslave\unity\build\Runtime/Export/Debug.bindings.h Line: 45)

Change Magic

(Filename: C:\buildslave\unity\build\Runtime/Export/Debug.bindings.h Line: 45)

Change Magic to first one

(Filename: C:\buildslave\unity\build\Runtime/Export/Debug.bindings.h Line: 45)

Change Magic

(Filename: C:\buildslave\unity\build\Runtime/Export/Debug.bindings.h Line: 45)

Change Magic to first one

(Filename: C:\buildslave\unity\build\Runtime/Export/Debug.bindings.h Line: 45)

Change Magic

(Filename: C:\buildslave\unity\build\Runtime/Export/Debug.bindings.h Line: 45)

Change Magic to first one

(Filename: C:\buildslave\unity\build\Runtime/Export/Debug.bindings.h Line: 45)

Change Magic

(Filename: C:\buildslave\unity\build\Runtime/Export/Debug.bindings.h Line: 45)

Goes Back

(Filename: C:\buildslave\unity\build\Runtime/Export/Debug.bindings.h Line: 45)

Save Current State.
-----------

Despite some annoyances, I really liked the game and I would love to finish my session after a fix.

Hey Amplify_ricardo,

Is there any update on this? Did you manage to reproduce the bug with the savegame I send? Are there any clues about why and where this goes wrong?

I wouldn't mind starting a new game if you conclude the chance is very low I encounter it in a new playthrough.
Due to lack of time, the thought of spending hours just to get blocked at the same spot with the same bug prevents me from trying it out at the moment (The steam user I referred to had it happen the same way on a second playthrough).

Any updates on this issue?

And except for the ones I linked to before, so at least 3 people have had this issue.
But I can imagine it is hard to track down with so few occurences.