I was not sure about the situation, so waited for a report or an e-mail with some clarification
E-mail is generally much faster and preferred
Generally (as described in different topics) the short self test, extended self tests are hardware self tests, running "inside" the hard disk drives, completely out of control of any software.
Hard Disk Sentinel can only
- start the test and
- read the progress
- check and interpret the results
But the test is done "inside" the disk drive, so everything (for example how long it runs) depends on the disk drive only. Sometimes other factors (eg. disk controller or its driver or USB adapter if used) can affect the response of the drive. Sometimes a different controller, different USB adapter or just a chipset update may change the behaviour.
Usually a software re-install makes no difference, so probably it was a coincidence only.
This is also described in the Help: sometimes these hardware self tests have their limitations and in this case a different type of test (Disk menu -> Surface test -> Read test) is recommended instead.
As usual, if you use Report menu -> Send test report to developer option, I can check the actual situation: examine the disk connection and driver used - and this may give some thoughts too.