Which autocomplete - Cursor Tab ghost text (gray suggestion) or the VS Code dropdown suggest widget?
File type - what language/file were you editing?
A specific example - what you typed, what was suggested, and what got inserted. A short screen recording would be ideal.
Also worth checking: System Settings > Keyboard > Text Input > Text Replacements on macOS — a similar report turned out to be caused by a text replacement rule there.
I’ve passed it to the team to fix. As a quick workaround for now, typing the word out fully (or just lowercasing the first letter after accepting) avoids it.
We’ll take a fresh look, but I would also like to point out that if the behavior is really getting in the way, you can disable the autocomplete entirely (Cursor Settings → Agents → Conversation → Agent Autocomplete).