Option plus arrow keys no longer moves by word
I was using my Mac Mini normally for most of the day, then quite suddenly, option plus left and right arrow keys stopped working. Normally, they move by word, but this no longer happens. They don't make a sound. Shift plus option plus arrow also does not select by word. I first noticed the issue in Scrivener, but quickly verified that all applications are affected, including TextEdit and the Safari address bar.
I found an older discussion describing this same problem. Following the advice in that article, I tried another user account, where option plus arrow worked normally. The article advised me to try safe mode, but unfortunately VoiceOver doesn't work in safe mode, so it's impossible for me, as a blind user, to try safe mode. If I understand correctly, the fact that the problem is limited to my specific user account indicates that reinstalling MacOS would not help.
Because This happened rather suddenly in the course of normal web browsing and word processing, it seems unlikely that some new login item has caused the issue, as I was not installing software.
Given that I can't try safe mode due to VoiceOver limitations, what other steps can I take to troubleshoot this issue?
My Mac is up-to-date with Sonoma 14.4.1.
Mac mini, macOS 14.4