A long EuiComboBox option seems to cause width issues where its parent EuiFlexItem no longer respects the width constraints imposed on it from EuiFlexGrid/EuiFlexGroup.

Here is a CodeSandbox demo using EuiFlexGroups, the first one is with a short option which causes no wrapping issues. The second uses a long option and you can see that the parent EuiFlexItem wraps into a new row:

Example use case in our plugin. For now, I will be fixing this using a calculated max-width on the EuiFlexItem: