Dynamics 365 Upgrade Mistakes: 3 Problems We See Again and Again
October 1, 2026
Most Dynamics 365 upgrade mistakes don't start during the upgrade itself. They start months or even years earlier with decisions that made sense at the time but were never revisited. The upgrade simply becomes the moment those hidden risks finally surface.
In this article:
The Pattern We Keep Seeing
Across upgrade projects, three Dynamics 365 upgrade mistakes account for most of the issues we get called in to investigate:
1. Skipping Sandbox Testing
When timelines become tight, sandbox testing is often treated as optional.
Unfortunately, this is usually the stage that reveals broken integrations, unexpected process changes, security issues, and customization conflicts before they reach production. Skipping a proper test cycle rarely saves time. It simply moves the risk to go-live.
2. Undocumented Customizations
Many Dynamics 365 environments contain customizations created years ago by consultants, partners, or employees who have since left the business.
Without clear documentation, teams often struggle to answer basic questions:
Why was this customization created?
Who owns it?
Is it still being used?
Will the upgrade affect it?
An upgrade readiness review frequently uncovers customizations that nobody currently understands well enough to assess.
3. Security Role Drift
Security roles are usually well designed when a system launches.
Over time, however, users change jobs, departments evolve, and access requests are granted to solve immediate problems. Eventually, the current security model no longer reflects how the business actually operates.
During upgrades, these gaps often become visible for the first time, leading to access issues, compliance concerns, or unexpected user disruptions.
Why These Dynamics 365 Upgrade Mistakes Keep Happening
None of these problems are technical failures.
They're process and governance issues that accumulate over time:
Testing gets compressed when deadlines slip.
Documentation gets postponed because the system still works.
Security reviews are deprioritized in favor of more urgent initiatives.
A Dynamics 365 upgrade doesn't create these issues. It simply forces teams to examine areas that may not have been reviewed for years.
Upgrade Readiness Checklist
Before starting your next upgrade, verify that you can answer "yes" to the following questions:
Does every customization have a clear owner who understands its purpose?
Have security roles been reviewed recently?
Does the sandbox environment accurately reflect production?
Is there a documented rollback plan for integrations and customizations?
Have critical business processes been tested against the target version?
If the answer to any of these questions is "no," you may already be exposed to some of the most common Dynamics 365 upgrade mistakes.
What To Do Before You Upgrade
The most effective mitigation steps are usually straightforward:
Make sandbox testing a mandatory part of the project.
Document customizations before the upgrade begins.
Review and validate security roles as part of upgrade planning.
Test integrations and business-critical processes early.
Identify ownership for every major customization and workflow.
These activities require effort upfront, but they are significantly less expensive than troubleshooting issues after go-live.
Related Reading
If you're planning an upcoming upgrade, these topics are worth reviewing next:
Data migration risks before a Dynamics 365 upgrade
Security role audits and access governance
Upgrade testing strategies for Dynamics 365 environments
When to Bring in Outside Help
If your team cannot fully account for existing customizations, lacks a reliable test environment, or is working against an aggressive timeline, it may be worth conducting an upgrade readiness assessment before the project begins.
At D365Apps.Support, we regularly help organizations identify common Dynamics 365 upgrade mistakes before they impact production environments. A structured readiness review can uncover risks early, reduce upgrade delays, and help your team approach go-live with confidence.
Think one of these issues might already exist in your environment? Contact D365Apps.Support for an upgrade readiness assessment before your next Dynamics 365 upgrade.
