Most of the keys work in combination with AltGr+Alt+[key]. The not working exceptions I found are y and . (period). I am following this instruction (https://www.autohotkey.com/docs/KeyList.htm#SpecialKeys Step 1 to 5) in order to analyze the problem.
Log output for AltGr+Alt+x (my AHK script is working with that shortcut)
A2 01D d 11.34 LControl
A5 138 d 0.00 RAlt
A4 038 d 0.13 LAlt
58 02D d 0.20 x
58 02D u 0.13 x
A2 01D u 0.17 LControl
A5 138 u 0.00 RAlt
A4 038 u 0.00 LAlt
Log output for AltGr+Alt+y (my AHK script is NOT working with that short cut)
A2 01D d 1.89 LControl
A5 138 d 0.00 RAlt
A4 038 d 0.05 LAlt
A2 01D u 0.36 LControl
A5 138 u 0.00 RAlt
A4 038 u 0.06 LAlt
This log output leads me to believe, that the problem is not my script, but something more global. It seems that AHK is not even receiving the key stroke for "y".
Log output for AltGr+y to prove that my keyboard isn't defective :)
A2 01D d 10.27 LControl
A5 138 d 0.00 RAlt
59 02C d 0.23 y
59 02C u 0.13 y
A2 01D u 0.17 LControl
A5 138 u 0.00 RAlt
Can any of you reproduce this? How can I use AltGr+Alt+Y as a shortcut? I am using Win10 x64 and AHK Version 1.1.30.01.
Edit
Obviously, the issue is only on my computer. So I would like to change the question slightly into: How can I identify and eliminate the reason that blocks some hotkeys? Remember that AltGr+Alt+Y is not the only hotkey that does not work, also AltGr+Alt+. and AltGr+Alt+O and possibly more that I have not tested yet.
~<^>!<!y:: MsgBox, LAlt+AltGr+y
(works this way on my system) – user3419297