SCCM- Upgrade from 2409 to 2509 WSUS timeout issue

The error 0x80244010 (WU_E_PT_EXCEEDED_MAX_SERVER_TRIPS) generally means that the Windows Update Agent exceeded the number of allowed round trips while retrieving update metadata from WSUS. It isn't usually caused by the ConfigMgr upgrade itself, but rather by the amount of update metadata the client has to process.

Since the issue only occurs during a Task Sequence and not during normal Software Center update scans, I would focus on the Software Updates scan performed within WinPE or immediately after the OS installation.

A few things I'd check:

Review the client logs

Look at:

WUAHandler.log

ScanAgent.log

UpdatesDeployment.log

UpdatesHandler.log

CAS.log

LocationServices.log

The logs should indicate whether the timeout occurs during the scan, metadata retrieval, or content download.

Verify the SUP synchronization

After reinstalling the Software Update Point, ensure that:

WSUS synchronization completed successfully.

wsyncmgr.log contains no errors.

WCM.log shows the SUP is healthy.

WSUSCtrl.log reports the SUP as healthy.

Check the Products and Classifications

Even if only a few products are selected, thousands of update revisions can remain synchronized.

For example:

Superseded updates

Feature Updates

Drivers

Preview Updates

Multiple Windows 10/11 releases

can significantly increase metadata returned to the client.

Review the Software Update Groups used by the Task Sequence

If your Task Sequence references "All Software Updates" or a very large Software Update Group, the scan can become much more expensive after an upgrade.

Try deploying a Software Update Group containing only a handful of recent cumulative updates to determine whether the issue is related to metadata size.

Run WSUS maintenance

Besides declining expired and superseded updates, verify that the WSUS database has been reindexed after cleanup.

Also verify that IIS application pools for WSUS are healthy and not recycling during scans.

Client version

After upgrading to 2509, verify that the boot image and Task Sequence are using the new ConfigMgr client version.

Update the boot images and redistribute them to all Distribution Points. A mismatch between the upgraded site and older boot images can sometimes produce unexpected behavior during OSD. 

Since the problem started immediately after upgrading to 2509, I would also verify that the Configuration Manager client and boot images have been updated and redistributed. Task Sequences rely on the boot image and client binaries, so if they're still using components from the previous version, software update scans during OSD may behave differently even though Software Center works normally. 

Also, 700+ applicable updates for Windows Server 2016/2019 and Windows 10/11 is higher than expected in a well-maintained environment. I would review:

Whether superseded updates are still deployed.

Whether the Task Sequence is scanning against multiple Software Update Groups.

Whether Feature Updates, Preview Updates, and multiple product versions are synchronized unnecessarily.

A smaller, well-maintained Software Update Group should significantly reduce scan time and WSUS round trips.