Magic keyboard suddenly typing the wrong characters

Agency14 wrote:

When I type a question mark I get _ and when I try to use an apostrophe I get [.

You have the Latin American Spanish Input Source active instead of an English one. Go to system preferences > keyboard > input sources and make sure you have only one item on the list, and that the name of that item is US or ABC. Remove Latin American or anything else.

Tesserax wrote: one or more of the following may be the reason:

You might want to add Wrong Input Source to your list. This particular one is pretty common in my experience, also in iOS

iPad Pro key board types wrong keys - Apple Community

Possibly, one or more of the following may be the reason:

• There is minute debris lodged between the keys and the keyboard surface.
• The keyboard had earlier experienced a liquid spill which has left conductive material that could affect one or more keys functionality.
• The keyboard is defective.
• The keyboard cable (wired keyboard only) is defective.
• The Mac's logic board / Bluetooth is faulty.

If resetting the keyboard does not resolve the issue, the next step would be to contact Apple Support directly for further assistance with this matter. To do so, simply select the "Support" link on the lower left-hand side of this forum's web page.

Excellent point Tom! Thanks, added it to my list for future reference.