Hi @DeepCoTech,
A process like this one may help to save most of the cable length.
I’m unsure how much of an effect the heat would have on the cable jacket, so I’d still err on the side of installing the new penetrator further up than where the old one was 
There are some other posts around the forum on potted splicing that you can search for, although I expect the effort and resources required are difficult to justify over attempting to remove the original penetrator and putting a new one on the cable.
Keeping a splice on the inside of the enclosure would be simpler and less failure prone than an external one (since you don’t need to focus on waterproofing). It would still require some additional wire and heat shrink though, and may make cable management a bit trickier inside the enclosure.