Scaler 3 corruption trying to spawn a popup modal window

Scaler 3 Support
1

I’m getting the following error …

Translated Report (Full Report Below)

Process: Scaler 3 [42850]
Path: /Applications/Scaler 3.app/Contents/MacOS/Scaler 3
Identifier: com.scalermusic.scaler3
Version: 3.3.2 (3.3.2)
Code Type: ARM-64 (Native)
Role: Foreground
Parent Process: launchd [1]
Coalition: com.scalermusic.scaler3 [88806]
User ID: 501

Date/Time: 2026-09-30 10:32:30.9376 -0500
Launch Time: 2026-09-30 10:30:15.9461 -0500
Hardware Model: MacBookPro18,4
OS Version: macOS 27.0 (26A428)
Release Type: User

Crash Reporter Key: 85A5A87B-5457-C9B7-5554-13FF9C3418A5
Incident Identifier: A1E25DED-C5DE-484F-B229-129743BE34A8

Sleep/Wake UUID: FADAB5C1-7194-4F18-99B9-03C1554D1064

Time Awake Since Boot: 970000 seconds
Time Since Wake: 433794 seconds

System Integrity Protection: enabled

Triggered by Thread: 0 JUCE Message Thread, Dispatch Queue: com.apple.main-thread

Exception Type: EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000

Termination Reason: Namespace SIGNAL, Code 6, Abort trap: 6
Terminating Process: Scaler 3 [42850]

Application Specific Information:
abort() called

Thread 0 Crashed:: JUCE Message Thread Dispatch queue: com.apple.main-thread

2

Hi @nsteblay welcome to the forum. Sorry to hear this is happening.

Is this something that only started occurring after updating to Scaler version 3.3.2?

It looks like this crash is when running Scaler 3 standalone. Are you having any issues when running Scaler 3 as a plugin?

Most standalone issues can be resolved by deleting the standalone state file located at: /Users/[NAME]/Library/Application Support/Scaler 3.settings

If you’re able to share the above mentioned standalone state file with us we can take a look to see what is going wrong, but hopefully deleting the file will resolve the issue for you regardless.

3

Hi,

I haven’t used it for a while. I have an M1 Macbook Pro with the latest O/S. I’ve deleted all directories and reinstalled it without any plugins. It still crashes. I’m running it standalone.

This is what I get from AI …

The crash was triggered by a heap corruption fault inside macOS’s memory allocator while Scaler 3 was trying to spawn a popup modal window.

1. Root Cause Breakdown- The Trigger Action:

Frames 18–21 show you clicked a button to open settings:

Plaintext

juce::StandalonePluginHolder::showAudioSettingsDialog()
juce::DefaultDialogWindow::DefaultDialogWindow(...)

  • The Faulting Subsystem:

    When JUCE (the C++ audio framework Scaler uses) creates a new window, it registers screen refresh timers with macOS using CVDisplayLink across all active displays:

    Plaintext

    juce::PerScreenDisplayLinks::refreshScreens()
CVDisplayLinkCreateWithCGDisplay
_CFRuntimeCreateInstance
_xzm_xzone_malloc_freelist_outlined

  • The Crash Point:

    Plaintext

    BUG IN CLIENT OF LIBMALLOC: memory corruption of free block
Exception Type: EXC_BREAKPOINT (SIGTRAP)

    libsystem_malloc detected that a pointer on its freelist had been overwritten or corrupted by a previous heap overflow/use-after-free elsewhere in the process. When CoreFoundation attempted to allocate memory for the new CVDisplayLink instance, the allocator hit the corrupted block and deliberately trapped out (SIGTRAP) to prevent arbitrary memory execution.

2. Contributing Environment Factors- Multi-Display Refresh Sync Across Differing Refresh Rates / Resolutions:

The system profile shows three distinct displays attached:

  1. Built-in Retina (3024 x 1964, ProMotion 120Hz variable)

  2. Samsung 5K (5120 x 2880, 60Hz)

  3. Asus MX279 (1920 x 1080, 60Hz)

JUCE’s display link loop (juce::PerScreenDisplayLinks) iterates over connected screens (NSScreen) to create separate display links. Multiple display-link threads (Thread 16 through Thread 19) were already active. JUCE has known race conditions when tearing down or registering per-screen display links while opening dialog windows across multi-monitor setups with mismatched refresh rates.

  • macOS Hardened Allocator Checks:

    The system is running on Apple Silicon with macOS memory zoning (_xzm_xzone_malloc). Modern versions of libsystem_malloc aggressively abort whenever a freelist pointer checksum fails rather than allowing undefined behavior to proceed silently.

3. Immediate Workarounds & Fixes1. Disconnect External Monitors to Configure Audio:

  • Unplug the external monitors (or test on just the built-in MacBook Pro display).

  • Launch Scaler 3 standalone, open the Audio / MIDI Settings dialog (which caused the crash), select your desired audio interface/buffer size, and close the dialog.

  • Reconnect the external displays. Scaler stores these settings in a .settings XML file, so you rarely need to open that dialog again once configured.

  1. Run as a Plugin (AU/VST3) in a DAW:

    • The crash specifically occurred in juce::StandalonePluginHolder::showAudioSettingsDialog(). This code path only exists in the standalone application wrapper.

    • Running Scaler 3 inside a host DAW (like Logic Pro) completely bypasses StandalonePluginHolder and JUCE’s standalone window-management peer, avoiding this specific crash path.

  2. Manually Reset Scaler Preferences:
    If the app crashes immediately upon opening the settings dialog due to a corrupted window geometry or audio state cache, reset its standalone configuration file:

    Bash

    rm ~/Library/Application\ Support/Scaler\ 3/Scaler\ 3.settings
# Also check:
rm ~/Library/Preferences/com.scalermusic.scaler3.plist

  3. Toggle ProMotion / Refresh Rate Lock:
    If the multi-display issue persists when opening secondary floating windows, go to System Settings > Displays and temporarily set the built-in liquid Retina display to a fixed 60 Hertz rather than ProMotion. Matching display refresh rates across all three heads prevents certain JUCE display-sync teardown race conditions.

Nick

4

It doesn’t crash when used as a plug-in for Logic Pro. I really can’t unplug my monitors so I just can’t run it stand alone right now.

Nick

5

Hi @nsteblay thanks for the update. If the crash is only occurring when running standalone the most likely issue is a corrupt standalone state file.

You did mention:

But please note that the standalone state file does not reside inside a Scaler 3 folder, but is inside your User Library - Application Support folder:

/Users/[NAME]/Library/Application Support/Scaler 3.settings

So would you mind please confirming that you have deleted the above file? This should resolve your standalone crash.