This issue can present as a timeout error when loading the list opened by a process. Typically, this issue is caused by the field list added to the process.
To troubleshoot this, you can start by assigning a standard field list to the process to test. You can also check the standard variant in a standard menu set. If the error is not generated, then the field list added to the process needs to be reviewed.
You can either remove the fields one by one until the process loads correctly (this way, you identify which one is the one causing the timeout) or you could use a different field list (preferably a standard one).
To change the field list to a standard one in the test system first, as it will be easier to identify which field is causing the issue, you can follow the steps below.
In the Admin Tool, click Menus.
Double-click the menu set where this process is used.
Double-click the process.
Click People (List) and expand the User Interface tab.
Click Change next to View (where you can see [Name], [Person Number], [Job Title], [Team], [Effective Status], [System Effective Status], [...]).
Maximise this Field Lists window.
Select a different field list and click OK.
Click OK to commit the changes.
If you need to have the original field list, you will have to start removing the fields one by one until the process loads fine for both employees by following these steps.
Within the Admin Tool, click Field Lists.
Find the Listing field list by using the Description column.
Single-click it and click Create a copy of the selected field list. Double-click the grey highlighted copy. Give it a description so that it is obvious the purpose for which it is going to be used for. It will help you identify it more easily.
Click OK.
Go to the menu set and drill into it up until you get to the People (List).
Single click it and expand the User Interface tab. Click Change and select the copy you've created of the field list.
Click Apply and double click the People (List). A warning window will pop up to let you know that any changes made here will take effect in all the places where this is being used. As this is a new copy, you can click OK.
Start by selecting the fields that you don't usually see in your People lists and click the green arrow pointed to the left. Click Apply and try loading the website.
Repeat step 8 until the process loads fine.