After you Refresh Your Sandbox, users may report receiving an Internal Server Error upon attempting to update Opportunity records in the user interface. Alternatively, attempting to update the Opportunities via the API using Data Loader for example, will result in:
This is commonly caused by a point-in-time copy issue related to performing an action against Roll-Up Summary Fields that either modifies them or triggers recalculation during the sandbox refresh process.
As per the sandbox Setup Tips and Considerations documentation:
"A sandbox is not a point-in-time snapshot of the exact state of your data. Furthermore, we recommend that you limit changes to your production organization while a sandbox is being created or refreshed. Setup and data changes to your production organization during the sandbox creation and refresh operations can result in inconsistencies in your sandbox. You might detect and correct some inconsistencies in your sandbox after it is created or refreshed."
To help expedite resolution include the following details when creating the case:
Submit, update or clone a Case with Salesforce Support
000382663

We use three kinds of cookies on our websites: required, functional, and advertising. You can choose whether functional and advertising cookies apply. Click on the different cookie categories to find out more about each category and to change the default settings.
Privacy Statement
Required cookies are necessary for basic website functionality. Some examples include: session cookies needed to transmit the website, authentication cookies, and security cookies.
Functional cookies enhance functions, performance, and services on the website. Some examples include: cookies used to analyze site traffic, cookies used for market research, and cookies used to display advertising that is not directed to a particular individual.
Advertising cookies track activity across websites in order to understand a viewer’s interests, and direct them specific marketing. Some examples include: cookies used for remarketing, or interest-based advertising.