🖥️ rehearsal-mini · Rehearsal-Mac-mini.local · M4 Pro · 48 GB · macOS 15.7.4 Probed 18:45 to 19:05 PDT · Oct 8, 2026

✅ Fixed, nothing destructive

🔥 Two stuck background apps each pinned one CPU core at 100% for weeks.

Avid Link and UA Mixer Engine were spinning in loops, not doing real work. Both are stopped or restarted. Your Apollo Twin X is still connected.

Both buttons open the Control Room on Greg's Mac.

🧊 Why Activity Monitor looked calm

Before · 20 days

After the fix

Pinned at 99 to 100%Normal

🧮 This M4 Pro has 12 cores (8 performance, 4 efficiency). Two pinned cores are about 17% of the whole chip, so the total CPU graph and the Energy tab looked quiet. inference, moderate
🔎 Sorting the CPU tab by "% CPU" would have shown both apps near 99%.
🌡️ macOS logged no thermal warning. Apple silicon throttles quietly. pmset -g therm

✅ Stopped and off at login

✅ Restarted

Reading	Before	19:08, about 4 min after
📊 Load average (1 / 5 / 15 min)	2.51 / 2.37 / 2.45	1.15 / 2.07 / 2.33
💤 CPU idle	72.72%	88.85%
👤 CPU user	13.93%	2.22%
⚙️ CPU system	13.33%	8.91%
🎚️ UA Mixer Engine	99%	13.6%
🚫 AvidLink	99 to 100%	Not running, disabled at login Off

🏁 Top by CPU at 19:08: UA Mixer Engine 13.6%, kernel_task 4.3%, UAD Console 2.6%, WindowServer 2.0%, DropboxFileProvider 1.7%, UA Mixer Helper 1.4%.
⏳ The 5 and 15 minute load averages still include the hot period, so they will keep falling.
🌙 Sleep is still blocked by NDIAudio, powerd, sharingd and NDIAssistant.

Item	What we saw	Status
📦 Dropbox file provider	23 GB in memory. A restart brought it back to 22.6 GB in 3 minutes. Memory was 86% free, so no pressure.	Your call
📡 NDI Audio driver	Has kept the Mac awake for 355 hours to stream audio over the network. Intentional or not is unknown.	Check
⚙️ kernel_task	27 h of CPU over 20 days.	Normal

💡 To shrink Dropbox on this Mac, set the big Dropbox-RecordingClub folders to online-only or selective sync. Restarting it does not help. No action taken.

🔬 Avid Link, full trace

Process AvidLink, PID 533, Intel build running under Rosetta, started at boot.
Main thread stack: NSStatusBarButton rightMouseDown, then trackMouse, then _nextEventMatchingEventMask, looping forever. A stuck UI event loop.
Fix: launchctl bootout (process gone), then launchctl disable gui/501/com.avid.link.
The plist /Library/LaunchAgents/com.avid.avidlink.plist is untouched (RunAtLoad 1, KeepAlive 0).
Pro Tools was not running, only its crashpad handlers. Avid Link handles Avid account and updates.

🔬 UA Mixer Engine, full trace

PID 29994, up 20 days 5 h, 18,857 CPU minutes.
The "Socket" thread inside UAD-2 SDK Support spun in boost::asio timer_queue (get_ready_timers, remove_timer). A runaway timer queue, not audio work.
Fix: SIGTERM, then launchctl kickstart gui/501/com.uaudio.ua_mixer_engine. New PID 69958.
UAD Console quit when the engine went down, with no crash report. Reopened with open -a "UAD Console", new PID 70044.
system_profiler still lists the Apollo Twin X. UAD software 11.8.1, UAD Console 1.3.0.

📦 Dropbox and other readings

DropboxFileProvider, Dropbox 274.4.4841, account folder Dropbox-RecordingClub.
Before: 23 GB resident, 1.5% CPU. Restarted once under the standing order for memory hogs.
Within 3 minutes: 70 to 90% CPU rescan, then 22.6 GB physical footprint at 0% CPU.
NDI: Core Audio driver NDIAudio holds a "NDI real-time UDP sending" no-sleep assertion, 355 hours.
Load average 2.5 before the fixes, 3.1 during the Dropbox rescan.
Machine up 20 days 23 h at 18:45 PDT, user tinyroomstudios.

↩️ Rollback

Turn Avid Link back on at login, then reopen UAD Console if it is closed:

launchctl enable gui/501/com.avid.link
open -a "UAD Console"

No reboot, no sudo, no files deleted.

🚨 What to watch

If the fans ramp up again, run this on the rehearsal Mac and look for UA Mixer Engine or AvidLink near 99%:

top -o cpu

A UA Mixer Engine spike means the timer bug came back. Restart it the same way.

launchctl kickstart -k gui/501/com.uaudio.ua_mixer_engine