Office Performance Issues

Fix Microsoft 365 Excel Version 2405 Slow Startup Issue

Steve K Oct 1, 2026 868 views

Question details

Users experience prolonged startup times when opening large Excel workbooks containing multiple links to other spreadsheets after updating to version 2405.

How to Fix Microsoft 365 Excel Version 2405 Slow Startup

Product: Microsoft 365 Excel
Device & OS: not provided
Scenario: Opening large workbooks that contain numerous external links.
Observed behavior: Excel takes several minutes to open the linked workbooks due to a suspected regression bug in the version 2405 feature update.

Before you start

Before making changes to your Office installation, verify your current build version via File > Account, and consider temporarily disabling external links to test if performance improves.

Solution 1Recommended

Roll Back Office to an Earlier Supported Build

Revert to a previous, stable version of Microsoft 365 to bypass the regression bug in version 2405.

Since this slow startup issue is a known regression in version 2405, the most effective temporary workaround is to revert your Office installation to an earlier build.

You will need to use the Office Deployment Tool or command line to safely roll back until Microsoft releases a permanent patch.

Disable Automatic Updates

Open Excel, navigate to File > Account, click on 'Update Options', and select 'Disable Updates' to prevent Office from immediately reinstalling version 2405.

Open Command Prompt as Administrator

Type 'cmd' into the Windows search bar, right-click on 'Command Prompt', and select 'Run as administrator'.

Execute the Rollback Command

Enter the appropriate Click-to-Run command to revert to your previous stable version. For example: '"%programfiles%\Common Files\Microsoft Shared\ClickToRun\officec2rclient.exe" /update user updatetoversion=16.0.xxxxx.xxxxx' (replace the x's with your target build number).

Roll Back Office to an Earlier Supported Build

Check Microsoft Documentation: Always refer to the official Microsoft Support documentation to find the exact build numbers for your specific update channel before executing the rollback.

Solution 2

Temporarily Disable Automatic Workbook Links

Prevent Excel from automatically updating links upon opening to speed up the application's startup process.

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If Microsoft 365 bugs are slowing down your workflow, consider switching to WPS Office. It provides a highly compatible, lightweight alternative for handling large workbooks and complex spreadsheets without the sluggish startup times.

1. Download WPS Office: Visit the official WPS website to download and install the free suite.
2. Open WPS Spreadsheets: Launch the application and select the Spreadsheets module.
3. Load Your Excel File: Open your large workbook to experience optimized loading times without performance regressions.

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Frequently Asked Questions

Why is Excel version 2405 suddenly so slow?

Version 2405 contains a known regression bug that specifically affects workbooks with multiple external links, causing the application to take several minutes to process and open these files.

Will I lose my data if I roll back my Office version?

No, rolling back the Office application version only changes the software build. Your saved workbooks, data, and settings will remain intact, though it is always recommended to create a backup beforehand.

How do I know when it's safe to re-enable Office updates?

Keep an eye on the official Microsoft 365 release notes. Once Microsoft confirms that the external link regression bug has been patched in a version subsequent to 2405, you can safely re-enable automatic updates via File > Account.

Does disabling external links permanently break my workbook?

No, disabling automatic updates for external links only prevents Excel from refreshing the external data during startup. You can always manually refresh the data links once the workbook is successfully opened.

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