Game Freeze/Stutter/Lockup via CPU Core 0 being held hostage

General Issues and Bug Reporting
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Summary

Issue appeared sometime after 2026-03-01, the first of March.
Playing a normal session in either LEGO Fortnite, Creative (UEFN), Reload, or selecting any of those game modes then disconnecting to go to the browse the lobby store will result in the CPU Core 0 is being held hostage at 100%. This locks up the PC, and only allows normal PC operation once per second-ish. Audio becomes completely slow and robotic even from sources not from the game. Symptoms appear after around 10 seconds to 60 minutes within an active game mode. Only remedy has been to force shut down PC and restarting. Force closing the game does not free CPU Core 0, and will not restore normal PC operation.

Evidence:

  • With every Game Latency Debuggers active, the high stutter and high ms that appears comes from the Game label.
  • Task Manager and Resource Monitor shows only CPU Core 0 at 100% while rest of the PC hardware is sitting between 0-50% usage.
  • I shut off every non-Microsoft service on my PC including all startup apps (aka Clean Boot testing). Then reboot. The game will play normally within a map for around 40 minutes before symptoms appear again. Normally, symptoms appear within 1 minute of launching into a match or mode on a normal/non-clean boot.
  • Other Unreal Engine 5 games like Satisfactory have no such issues even after 10 hours of continuous gameplay. (This was tested 2 days ago)
  • Event Viewer reports no errors nor warning at the time of symptoms appearing
  • CPU and GPU temperature normal (75 degrees C/55 degrees C) before and during lock up.

Remedies I’ve tried:

  • Uninstalled Fortnite and deleted %localdata% of FortniteGame, Anticheat, Anticheat_EOS. Restalled after reboot
  • Uninstalled graphic card driver within safe boot using Display Driver Uninstaller (DDU). Rebooted into normal mode and reinstalled studio driver from Nvidia
  • Disabled Nahimic
  • Disabled audio enhancements
  • Nvidia Low Latency Mode set to ON
  • Nvidia Power Management set to Prefer Max Performance
  • Set Power Plan to Max Performance
  • Disabled HAGS
  • AMD Chipset update
  • Updated Windows System Files, and motherboard/component drivers
  • Verified Game files within epic launcher
  • Cleared Shader cache
  • DISM repair (component store was damaged, repaired)
  • SFC scan (clean after DISM repair)
  • EAC repair
  • Performance Mode Rendering and is in windowed fullscreen
  • FPS Capped at 240
  • Changed Rendering Modes from Performance to Performance (Legacy)
  • Reviewed PC Hardware issues like CPU heat throttling or RAM Memory leaks using Latencymon and HWiNFO64
  • Consulted Claude 4.6 Thinking on any missing steps or ideas as to the causes.

My novice understanding of Fortnite logs and asking Claude shows LogFortHitches: HITCHHUNTER being triggered every other line from completely disjoint causes for 1000.0 ms every frame.

I can include the Latencymon results and Fortnite Logs if needed. I could only take a snapshot on my phone because Latencymon is unable to export when PC is locked up. It’s largely ntoskrnl.exe showing 998ms execution.

Please select what you are reporting on:

Creative

What Type of Bug are you experiencing?

Stability

Steps to Reproduce

Load into any CREATIVE game mode, or Reload, or LEGO Fortnite session
Wait around 10 seconds to anywhere around 50 minutes
The PC will begin to lockup.

Expected Result

The PC won’t lock up

Observed Result

The game becomes completely unplayble, only allowing normal operation once every second.

Platform(s)

PC

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Additional Notes

It was recommended by people within the Epic developer community to make a post here even though it’s not exclusively a Creative issue. An older version of this bug report has been posted to this thread on the Official Fortnite Discord forum: Discord