I believe you have a bug in your software.
I would like to display a 2 digit hour value, but want the time displayed in 24hour format. So I'd like the hour zero padded if it is less than 10.
Here are the value and format combinations I've used and how to recreate the bug:
5/1/2018 1:11 => dd-mmm-yyyy h:mm => 01-may-2018 1:11 (works)
5/1/2018 1:11 => dd-mmm-yyyy hh:mm => 01-may-2018 01:11 (works)
5/1/2018 13:13 => dd-mmm-yyyy h:mm => 01-may-2018 13:13 (works)
5/1/2018 13:13 => dd-mmm-yyyy hh:mm => 01-may-2018 01:13 (broken)
Let me know if you have any questions.