Error calling a tree structure method (Tree Control)

What causes this issue?

An error occurred while calling a method of the tree control.

System Response

This may cause navigation problems or reduced selection options.

How to fix this error?

Restart the workload monitor. If the error persists, check your
frontend installation.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.