Why am I hearing my voice overlapping itself in my headphones

Hi! Recording newbie, using Studio One 3 Prime.

For some reason, I have suddenly started hearing what seems to be an overlap of my own voice in my headphones when monitoring my microphone channel. Actual recordings sound correct (no extra voice), but while monitoring the input to check levels, it's as though there are two of me speaking at roughly the same volume. It started happening fairly suddenly after adding a track, but I do not know what setting I might have changed, or if there is something else amiss. I have powered off the computer and audio interface and restarted both, but the behavior remains. And it isn't exclusive to a single song file. It is now the behavior regardless of what song I have opened, even brand new ones.

I find the effect reminiscent of the very beginning of the song "Cannonball" by The Breeders.

I am confident that this isn't a headphone bleed situation because when I actually record my voice the playback sounds correct (I am not getting the "ghost" voice").

Steps I can take to reproduce the effect at any time:

Start Studio One 3 Prime

Create new song

Add track

Activate monitoring on the new track

Speak into microphone. Hear overlapping voices.

Computer Make and Model: Self built. Gigabyte X299 UD4 motherboard w/ Intel i7 7800X 16 GB RAM

Operating System and Version: Windows 10 Pro 64 bit

Application Version: 3.5.6.46910

Audio Interface and it's Driver Version: Focusrite Clarett 8Pre Thunderbolt v4.25.0.335

Digital Mixer and it's Driver/Firmware Version: No mixer hardware (unless the 8Pre counts)

Microphone: Shure Beta 57A