Issue Migration Failure: Classic to Integrated Mode Conversion Fails Due to UTF-8 Decode Error

[Rabah]

Server operating system version

Windows Server 2022

Plesk version and microupdate number

Plesk Obsidian 18.0.70 Update #3 Web Host Edition

Hi,

We’re facing a migration failure during conversion of Classic app pools to Integrated mode, matching the issue described here: Failed to allow applications in Classic to work in Integrated mode after migration in web.config files

Migration Scenario:

I'm running a migration using Plesk Migrator:

• Source Server: Windows Server 2012
• Target Server: Windows Server 2022

Observed Error Logs (from Plesk Migrator):

Failed to allow applications in Classic to work in Integrated mode after migration in web.config files
Migration tools tried to perform operation in 3 attempts: 'utf-8' codec can't decode byte 0xff in position 57: invalid start byte

Debug Messages:

2025-08-05 15:17:43 Exception
Exception:
Traceback (most recent call last):
File "C:\Program Files (x86)\Plesk\admin\plib\modules\panel-migrator\backend\lib\python\parallels\core\safe.py", line 191, in try_subscription_with_rerun
func()
File "C:\Program Files (x86)\Plesk\admin\plib\modules\panel-migrator\backend\lib\python\parallels\core\workflow\runner\by_subscription.py", line 526, in <lambda>
lambda: action.run(self._context, subscription),
File "C:\Program Files (x86)\Plesk\admin\plib\modules\panel-migrator\backend\lib\python\parallels\core\actions\fix_web_config_integrated_mode.py", line 134, in run
runner.execute_command(
File "C:\Program Files (x86)\Plesk\admin\plib\modules\panel-migrator\backend\lib\python\parallels\core\runners\base.py", line 131, in execute_command
str_decode(execution_results.stdout, output_encoding),
File "C:\Program Files (x86)\Plesk\admin\plib\modules\panel-migrator\backend\lib\python\parallels\core\utils\common\string_utils.py", line 119, in str_decode
return s.decode(encoding)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xa0 in position 57: invalid start byte

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "C:\Program Files (x86)\Plesk\admin\plib\modules\panel-migrator\backend\lib\python\parallels\core\safe.py", line 164, in try_subscription
yield
File "C:\Program Files (x86)\Plesk\admin\plib\modules\panel-migrator\backend\lib\python\parallels\core\safe.py", line 197, in try_subscription_with_rerun
raise MultipleAttemptsMigrationError(exceptions)
parallels.core.safe.MultipleAttemptsMigrationError: Migration tools tried to perform operation in 3 attempts: 'utf-8' codec can't decode byte 0xa0 in position 57: invalid start byte
2025-08-05 15:17:43 Error
Failed to perform an action on subscription 'example.com': Failed to allow applications in Classic to work in Integrated mode after migration in web.config files Exception message: Migration tools tried to perform operation in 3 attempts: 'utf-8' codec can't decode byte 0xa0 in position 57: invalid start byte

Diagnostics:

• Verified web.config file is UTF-8 encoded (no BOM).
• Inspected the flagged line, no unusual characters found.
• Hex-level analysis confirmed no invalid bytes at the reported offset.

Request:

Is there an updated patch or fix for this migrator issue (potential regression PMT‑5599)?

Thanks,

 

[Sebahat.hadzhi]

Hello, @Rabah . Considering that the source server is EOL issues could be expected. It is very unlikely for a patch to be released for that outdated version even if the root cause lays within the migrator. There was a similar bug that was fixed in version Migrator 2.26.11.