How can I tell if SCANPST.EXE is running when it does a repair?

You can use Outlook Repair Set. Outlook repair solution is designed for repairing damaged email folders in Outlook and fixing email errors, caused by disk issues, file system problems and other errors.

For more: https://www.outlookrepairkit.com/

If you are facing issues in accessing your important Outlook PST file data, then you need to recover the data instantly. To recover all the data you can use the Outlook PST file recovery tool to repair the corruption in the PST file and regain access to the file.
For more info, read - https://www.data-recovery-solutions.com/ost-to-pst-file-converter.php

Of course, ScanPST windows open on your screen at that time. It will give you a pop up after recovery. Better to restart your system after repairing any file. Since inbox repair tool is limited to resolve the minor error, Data Corruption cannot be resolved at such case. So, using a third party PST Repair Tool is not a bad option as it gives you too many perks like instant recovery of any file size, Easy to use, Bunch of file formats to save the data, preview of data without MS Outlook application. Still, it's demo version is Outstanding which is limited to some feature but better than the manual method. So, it's better to consider this tool for your backup and recovery purpose.

If you have any issue regarding corrupted PST file or your PST file get corrupted due to any of the reason and you have tried all the solution that you know like using an inbuilt tool Scanpst.exe Tool (Inbox repair tool) that gets installed along with the MS office suite etc only then the last solution that left is to go with Kernel Outlook PST Recovery recover all the lost/deleted/corrupted data files of Outlook. It provides you unique facility to recover all the damaged data along all personal folders & attachments.

Use Kernel for Outlook PST Recovery Software to access inaccessible Outlook PST file or email. It provides accurate solution without data loosing. You can run this third party software in all versions of MS Outlook. Get complete detail about this tool visit http://www.en.fixpst.net/

Right click on the task bar and start task manager
that will tell you what is running or not responding