Hello. A problem occurs on my computer. Sometimes (quite a few), the game speeds up, and the character teleports. I hope you can appreciate it in the attached video.
VIDEO: youtu.be/wUoHRSd-EAM?si=y1lB6e8QFq1cOUl2

I also have this issue unfortunately. Same thing as you. I have no idea why the game speed is being wonky...

Try to set 60hz of refresh rate and enable v-sync

Unfortunately, I did. 1920x1080 60hz with vsync enabled and nothing changed at all. Its so strange!

The old version was not playable because of this...

Yeah, wasn't that one of the things Gemini fixed? Or was it just fixed with Sourcenext.

Have also tried:

Manually setting my own monitor to 60hz
Limiting the executable to using only one CPU core
Forcing Vsync on through Nvidia control panel

This is the exact issue that I am getting too! So far nothing I have tried has worked in fixing the problem.

You're not alone, friend! Its definitely because its based on the Win95 version.

Came here to report the same issue, although it isn't nearly as bad as what I'm seeing in the attached video, it's more just like a little jerk in the knee, and it feels like she's moving slightly too fast, as if the animation is attached to frame rate. I'm going to try a few things in NVIDIA control panel and see if it helps (I'm running on a 2070).

It is attached to fluctuating framerate, back in the day we used to get around it by using an application to throttle a game's performance. I forgot what it was though.

The issue is with the game's code itself. Back in the mid 1990s, PC games' speed was tied directly to the old Pentium CPU speed. It was never conceived that we would have the multi-core processors that we have now at the speeds they work at. The result is that the game runs faster than originally intended. The only way to resolve this issue is, as has already been said, run a third party program to throttle the game to force it to run at the 30FPS it was originally meant to run at. The speed conflict is also the reason why there are minor sound synchronization issues.

Okay, observations:

Poking around in the DirectX Options exe that comes with the game, and in the NVIDIA control panel, here's what I've seen:

Running the game at 1440p with different versions of vsync causes different amounts of this animation stutter. With vsync turned off at 60hz, it's terrible. With vsync on at 60hz, it's noticeable but she doesn't seem to teleport from spot to spot. With vsync on at 30hz, the stutter is gone almost entirely. In fact, I only notice it right near the typewriter in the main hall. Throughout the rest of the room, I don't see it at all.

In the NVIDIA control panel, none of the vsync options seem to do anything differently with the in-game vsync turned off.

Finally, I went in and set the game compatibility mode to Windows 95, and I've set the in-game resolution (via the DirectX Tool in the game's install folder) to 1440p 30hz with vsync set to application controlled, and the issue is more-or-less gone. Haven't noticed it again yet.

Given that this issue is apparently in the original PC port, I imagine it's tied to the higher framerate. The game was designed to run at 30 fps on the PSX, so running at 60 fps on PC makes the character animation too fast, and the pacing of the animation goes apeshit and causes stutter (which is why it gets so much worse when I turn vsync off and let the frame rate jump even higher). Locked at 30, it now feels, to me, like I'm playing it on the PSX.

For now, the only solution appears to be: lock the game frame rate/refresh rate at 30.
Fortunately, the game comes with a built-in DirectX Tool that you can run that lets you set the resolution/framerate. Just pick your resolution and pick 30hz, and the issue goes away. In the attached screenshot are my in-game settings. It's playing just fine now, feels like I'm playing it back on the PSX.

I don't have 30hz with my monitor... I can only set 30 fps in driver control panel

Its been discovered that Gemini's RE Classic Rebirth patch that fixes the framerate issue on the original version also fixes it here without changing your monitor settings. I'm installing it now. You have to change the game to the JPN version.

I didn't realize there were monitors/TVs that don't support 30hz. I thought that was a basic industry standard.