It looks like !4423 (merged) was not enough. We also need to ignore combinations of Ctrl with other modifiers, i.e. Ctrl + Shift. For example, Ctrl + Shift + 6 is mapped to the character 0x1E on a US keyboard (but it should be treated as Ctrl + ^, with only Shift being consumed). Basically, always ignore Ctrl unless it is used in conjunction with Alt, i.e. as part of AltGr.