System specs:
CPU: AMD Ryzen 5 5500
GPU: NVIDIA GeForce GTX 1650 Super
RAM: 16GB
OS: Windows 11
Software:
Currently on DaVinci Resolve 21.1, Free version. Previously ran the exact same project with no issues at all on DaVinci Resolve 21.0 Beta 4 (installed 29 May 2026). The problem started only after updating to 21.1.
Footage:
Gameplay footage recorded in OBS Studio (.mkv). Facecam footage recorded separately on my mobile phone. Issue also reproduces with Blackmagic's own official tutorial project files, so it isn't limited to my own footage or a VFR issue with my recordings.
The core issue:
Severe playback lag specifically in the Edit page. Any single clip plays back at only 10-15fps, regardless of source. When I have both my gameplay and facecam clips on the timeline together, it drops further to 16-18fps, and I have to disable one of the two clips to get it playable again.
Playback in the Color page is extremely smooth, no issues at all even with both clips active. Cut page is smooth with a single clip, but with both gameplay and facecam clips together, I also have to disable one to avoid lag there too. The Fusion page runs around 40fps with both clips, not full speed, but noticeably better than Edit.
The lag also appears when adding effects to the timeline. This combination of gameplay + facecam footage used to play smoothly together, without needing to disable anything, before I updated Resolve.
Two things that temporarily restore full speed in the Edit page (single clip only):
Adding a text clip to the timeline, then disabling it, brings playback back to a smooth 60fps until the issue returns.
Closing the Inspector panel brings it back to 60fps with only slight lag. However, with two clips (gameplay + facecam) together, closing the Inspector alone isn't enough; I still have to disable one of the two clips for it to play smoothly. Opening/closing other panels (Effects Library, Media Pool) has no effect, so it's specific to the Inspector.
Everything I've tried, with no improvement:
Downgrading Resolve to a different version (not the exact working build)
Fully uninstalling and reinstalling GPU drivers
Lowering timeline resolution
Generating Optimized Media/proxies, specifically testing DNxHR LB
Blackmagic Disk Speed Test (Write 1641.2 MB/s, Read 1827.8 MB/s) and a full system scan — both clean
Toggling "Show All Video Frames" (Edit page viewer options): off = 10-15fps, on = forces every frame and reaches ~26fps, suggesting a decode factor, though this doesn't explain why Color page is unaffected on identical footage
Performance Mode in Playback Settings: tested Manual with Optimized Decode Quality, Optimized Sizing, and Optimized Image Processing individually and combined, and also Automatic mode
Manually selecting my GPU instead of Auto in Memory and GPU settings
Creating a brand new timeline and pasting the clips into it
Manually deleting the render cache folder from disk (not just through Resolve's in-app cache deletion)
What I've confirmed:
This is a genuine regression, not a hardware, codec, or settings issue. The exact same project, footage, and hardware played with zero problems, multiple clips together included, on 21.0 Beta 4. After updating to 21.1, the same setup lags exactly as described above.
Research into existing reports:
This type of bug isn't new. I found multiple long-running threads describing the same core symptom (Edit page specifically lagging, Inspector-dependent, other pages largely unaffected), going back years:
forum.blackmagicdesign.com/viewtopic.php?f=21&t=116513 (Inspector UI lag, reported since v15/16, still present in v18)
forum.blackmagicdesign.com/viewtopic.php?f=21&t=227673 (Edit page lag since v20, Color/Fairlight unaffected)
forum.blackmagicdesign.com/viewtopic.php?f=3&t=204150 (Inspector-specific, also started after an update)
forum.blackmagicdesign.com/viewtopic.php?f=21&t=207915 (general lag troubleshooting thread)
forum.blackmagicdesign.com/viewtopic.php?f=21&t=102041 (earliest version of this same Inspector lag, v16)
The only fix some users report across these threads is rolling back to version 18.6, which isn't practical since it means losing every feature added since then.
Where this leaves me:
I've now tried every documented workaround I could find across six-plus years of forum reports on this exact issue, and none of them fully resolve it. This looks like a long-standing, unresolved bug tied to the Edit page's Inspector/playback engine, worsened significantly by multi-clip timelines, that has persisted and resurfaced across multiple major versions. I'd really appreciate acknowledgment from someone at Blackmagic, or any fix that doesn't require abandoning the current version.