Suddenly unstable can’t hold fps after codec/driver changes

Hey guys, new to forum, but been using svp for about a year.

I sent in an email to support, but figured it may be worth asking here as well.

I’m seeing severe performance regressions with SVP 4 Pro + RIFE on a system that used to be rock-solid. I’d appreciate help verifying what has changed.

Environment
•    SVP 4 Pro: 4.7.0.302 (fresh reinstall)
•    Windows 11 23H2 (22631)
•    CPU: Intel i9-13900KS
•    GPU: NVIDIA RTX 4090
•    RAM: 64gb ddr5
•    NVIDIA driver: 576.88 (last known working version for me, clean install; also tried newer/older)
•    Player(s):
o    MPC-HC x64 (2.5.x) + VapourSynth Filter
o    MPC Video Renderer (D3D11; Catmull-Rom/Jinc2m/Lanczos; HDR passthrough)
o    LAV Filters: Video = DXVA2 (copy-back), NV12/P010/P016; Audio bitstream
o    Also tested MPV (—no-config)
•    Display: TCL QM8K 98", 3840×2160 @ 120 Hz, HDR10/DV (eARC to Nakamichi soundbar)
Problem
•    SVP + RIFE that previously held 120 fps at ~80% GPU now can’t hold even 60 fps on the same files.
•    SVP Index hovers ~0.2–0.4; sync offset in MPC climbs rapidly; frequent dropped frames.
•    GPU usage becomes erratic (0–100% oscillation) during SVP playback, while FurMark 2 (Vulkan) drives 98–100% stably — so hardware seems fine.
What changed right before the regression
•    Updated K-Lite (LAV/MPC-VR), then rolled back.
•    Updated NVIDIA driver, then DDU + reinstalled 576.88 (known-good previously).
•    Fully reinstalled SVP (including running only with SVP-bundled components).
What I’ve already tried (no improvement)
•    SVP:
o    Fresh install; verified VapourSynth path (AviSynth won’t hook RIFE).
o    Active profile = RIFE AI engine.
o    Settings show:
•    rife_engine = 1 (TensorRT)
•    rife_trt_model = 4.6
•    rife_threads = 2
•    rife_trt_boost = 1
•    rife_trt_gpu = 0
•    rife_sc = 10, rife_sc_method = 1
o    Deleted all *.engine / *.plan under …\rife\models\rife-v4.6\ to force rebuild.
•    Players / filters:
o    MPC-HC with only LAV Splitter/Video/Audio + VapourSynth Filter in chain.
o    LAV Video = DXVA2 (copy-back); outputs NV12/P010/P016; PC (0–255).  Tested DXVA2 Native, cuda, and d3d11, all same issue.
o    MPC VR D3D11; Adjust frame presentation time ON; Discard swap; Reinitialize device ON.
o    Tried EVR-CP as control — same result.
o    MPV (—no-config) + SVP — same stutter.
•    System:
o    Disabled Intel iGPU (UHD 770) during tests.
o    Windows desktop tested at 60 Hz and 120 Hz; HDR on/off.
o    HAGS OFF, VRR OFF, Game Mode OFF.
o    EDID/CRU fully reset; TV re-enumerated; output is stable 4K/120/10-bit outside SVP.
o    FurMark 2 Vulkan full-screen shows stable utilization/thermals (no throttling).
Current behavior
•    SVP Performance Monitor shows Index < 1.0 and low/oscillating GPU activity during playback.
•    Same content used to run perfectly at 120 fps with RIFE 4.6 (Perf mode ON, GPU threads = 2).
Questions / Help Requested
1.    How to fully reset SVP’s AI caches/backends beyond deleting .engine/.plan files?
o    Additional folders to clear?
o    Any flags to force re-build with a clean TRT runtime?
2.    Known regressions: Is there any known issue on Windows 11 22631 + RTX 4090 with SVP 4.7 + RIFE 4.6 TensorRT after recent K-Lite/LAV updates?
3.    Recommended baseline: Could you share a minimal, known-good RIFE (TensorRT) profile for a 4090 (target 120 Hz), including recommended:
o    rife_threads, rife_trt_boost, rife_sc, multiple_queues, any other GPU queue settings
o    Any MPC-VR/LAV specifics that are sensitive for TRT performance
4.    Verbose diagnostics: Is there a way to enable verbose TensorRT logging from SVP to confirm the engine path, precision, and any runtime fallbacks?
Attachments (can provide on request)
•    SVP log (fresh run from app start → engine rebuild → playback start)
•    profiles.cfg, frc.cfg, main.cfg
•    Screenshots: SVP “All settings” (rife block), MPC-VR settings, LAV Video settings, SVP Performance Monitor during stutter, MPC-VR OSD (Ctrl+J)

1080p remuxes work fine, but 4k remuxes that used to have no issue crawl at 6fps and video card is barely engaged - i've spent about 12 hours reverting trying to figure this out and i'm usually quite good with this stuff but I'm stumped atm.

Thanks in advance for any guidance. I’m happy to run specific builds or collect extra logs if that helps pinpoint why RIFE is no longer keeping sync on this setup.