parseDateTime($CurrentValue,'yyyy-MM-dd''T''HH:mm:ss') only works when 'yyyy-MM-dd''T''HH:mm:ss is the correct format. You now assume the date is formatted with '-' and looks like 2017-Sep-12 etc.
It should be more like parseDateTime($CurrentValue,'EEE MM hh:mm:ss yyyy')
You can check how you have to write your format in the links below:
parseDateTime($CurrentValue,'EEE MMM hh:mm:ss z yyyy')
This might work.
Your input contains redundant data, and I can imagine Java's SimpleDateFormat not wanting to have anything to do with a format that contains redundant data. What works for me is:
parseDateTime( substring($input, find($input, ' ')+1), 'MMM dd hh:mm:ss z yyyy')
This is supposed to strip out the " Tue " part from your input, the remaining String should parse fine.
Maybe the +1 in my line needs to be a +2, not completely sure there.
Edit: As Edwin rightly pointed out, my solution is wrong, it just works for this specific case where Sep is Sep in both Dutch and English but will fail for a date in May.
If running app in English language, format 'EEE MMM d HH:mm:ss z yyyy' should parse fine.
If running in another language like Dutch, 'Tue' is not recognized. Date formatted in Dutch with the same format will be something like 'di sep 12 22:18:36 GMT+02:00 2017
Using a Java action, you could specify the locale to be used when parsing a date.