Very choppy playback on 50% slow motion (50 fps → 25 fps) using ProRes Proxy in Premiere Pro 25.5

[ARR_VISUALS6423]

Hi everyone,

I’mhaving a strange and frustrating issue with Premiere Pro 25.5.

I shoot on a Sony A7 IV in 4K 50 fps, and I’m editing in a 25 fps sequence to create 50% slow motion.

Everything should be smooth — and the exported footage looks perfect — but the preview playback is extremely choppy.

 My system:

• CPU: Ryzen 7 5700X

• GPU: RTX 4070 (with CUDA enabled)

• RAM: 32 GB

• SSD: 1 TB NVMe

• OS: Windows 11

• Playback resolution: ¼

My workflow:

• Original clips: 4K 50 fps (H.264 10-bit)

• Proxies: ProRes Proxy 960×540, container QuickTime, “Match Source (frame rate)”

• Sequence: 25 fps

• No effects, no LUTs, no titles — just the raw proxy clip slowed to 50 %

 The issue:

• Playback is choppy only in the preview window, even at ¼ resolution.

• As soon as I render the selection, playback becomes perfectly smooth.

• Exported video is smooth as well.

• If I disable proxies, playback is also smooth (but i cant work without proxy because my pc will lag)

 What I’ve already tried:

• Re-created the proxies (ProRes Proxy — multiple times).

• Verified Mercury Playback Engine (CUDA) is enabled.

• Cleared and relocated the media cache to the SSD.

• Rolled back to Premiere 24.3, but couldn’t open the project (saved in 25.5).

• Tested playback with no speed change → smooth.

• Tested “Interpret Footage” to 25 fps instead of “Speed/Duration” → smooth.

 My hardware should have no issue reading ProRes Proxy 540p in real time.

Can anyone from Adobe confirm if this is a known issue in 25.5?

Is there a fix other than rendering or interpreting footage?

Or a safe way to roll a 25.5 project back to 24.3 without losing edits?

Thanks in advance to anyone who takes the time to reply 

This is a pretty standard workflow (4K 50 fps → 25 fps slow motion), so I imagine I’m not the only one seeing this.

Have a good day,

[Dani_V.]

Hi @ARR_VISUALS6423, 

Thank you for reporting a problem and for providing all these details.

If you import the proxy files on their own (with no source media attached), do they show the same issues, or is it only when they are attached and enabled? Do you see the same behavior if there are no speed changes applied to the files at all? 

Sorry for the frustration, 
Dani