isync service (i.e. mbsync) stops functioning but produces no logs for debugging

[cacology]

Output of brew config

HOMEBREW_VERSION: >=2.5.0 (shallow or no git repository)
ORIGIN: (none)
HEAD: (none)
Last commit: never
Core tap origin: https://github.com/Homebrew/homebrew-core
Core tap HEAD: (none)
Core tap last commit: never
Core tap branch: (none)
Core tap JSON: 16 Apr 14:18 UTC
HOMEBREW_PREFIX: /opt/homebrew
HOMEBREW_CASK_OPTS: []
HOMEBREW_DISPLAY: /private/tmp/com.apple.launchd.bk3593Jb5n/org.xquartz:0
HOMEBREW_EDITOR: /usr/local/opt/emacs-mac/bin/emacsclient -c
HOMEBREW_MAKE_JOBS: 12
Homebrew Ruby: 2.6.10 => /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/bin/ruby
CPU: dodeca-core 64-bit arm_blizzard_avalanche
Clang: 14.0.3 build 1403
Git: 2.39.2 => /Applications/Xcode.app/Contents/Developer/usr/bin/git
Curl: 7.87.0 => /usr/bin/curl
macOS: 13.3.1-arm64
CLT: N/A
Xcode: 14.3
Rosetta 2: false

Output of brew doctor

Warning: Some installed kegs have no formulae!
This means they were either deleted or installed manually.
You should find replacements for the following formulae:
  pycparser
  cffi

Description of issue

Calling brew services start isync as a non-admin user happily does what is expected: starts a instance of isync (i.e. mbsync) according to my files. However, after about 24 hours, it seems to stop working. I'd like to fix it so it doesn't periodically stall.

I've tried to debug it a bit, but cannot get it to produce log files. Can anyone advise?

What I've tried

Restarting it when it stalls works fine, so I wanted to look at the log files. As it is, it sends out and error to /dev/null so I wrote my own plist, i.e.

homebrew.mxcl.isync-log.plist:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>EnvironmentVariables</key>
	<dict>
		<key>PATH</key>
		<string>/opt/homebrew/bin:/opt/homebrew/sbin:/usr/bin:/bin:/usr/sbin:/sbin</string>
	</dict>
	<key>Label</key>
	<string>homebrew.mxcl.isync</string>
	<key>LimitLoadToSessionType</key>
	<array>
		<string>Aqua</string>
		<string>Background</string>
		<string>LoginWindow</string>
		<string>StandardIO</string>
		<string>System</string>
	</array>
	<key>ProgramArguments</key>
	<array>
		<string>/opt/homebrew/opt/isync/bin/mbsync</string>
		<string>-a</string>
	</array>
	<key>RunAtLoad</key>
	<false/>
	<key>StandardErrorPath</key>
	<string>/Users/james/Library/Logs/homebrew.mxcl.isyncerr.log</string>
	<key>StandardOutPath</key>
	<string>/Users/james/Library/Logs/homebrew.mxcl.isyncout.log</string>
	<key>StartInterval</key>
	<integer>300</integer>
</dict>
</plist>

Then I loaded this with brew services start isync --file=homebrew.mxcl.isync-log.plist. It didn't seem to be running. I tried /bin/launchctl bootstrap gui/503 /Users/james/Library/LaunchAgents/homebrew.mxcl.isync.plist which complained: Bootstrap failed: 5: Input/output error.

How can I get a useful log file for this running as a non-admin user? Or, even better, any ideas why isync might be choking over night?

[pmiam]

I have a similar problem. Just started using MacOS this week. brew service start isync creates the LaunchAgent file as expected, but the service immediately fails with brew services list status error 256.

Attempting tobootstrap the service with launchctl fails with the same error Bootstrap failed: 5: Input/output error for both root and my user 501. however enabling/disabling does appear to change the => status returned by launchctl print-disabled gui/501. This has no obvious effect.

[pmiam]

one possibility is that the daemon does not have access to my user's configuration file...