Having to double clutch with reverse?

[Thrash]

Hi guys, first post here! I got a Scirocco brand new at the start of this year and love it (some bits more than others, as I'll explain..!)
I'm having some issues with reverse gear, I had some reverse-parking sensors fitted when I picked up the car so they were fitted by a 3rd party I'm guessing, at the dealer, I have no idea if this is effecting it but thought its possible so worth mentioning.

I'm having to double clutch it most time I put it into reverse, it kept happening when I first got the car and I put it down to pilot error and the fact it was new, now its worn in a bit and ive gotten used to it, it still happens but seems to be rather random. What's happening is the parking sensors beep and it feels like its gone into gear; you cant push it any further, go to move off and it starts grinding so you either really shove it or double clutch it (like I had to in my old car!), but as I say its quite random usually when I first get in the car when its cold but when I drive somewhere and reverse park for example there's no problem at all.

Its still covered under warranty and I can just go back to the dealer but I know they will get in, try it and say there's no issue and its pilot error. This is mainly because it will have warmed up by then and it doesn't usually happen then but also because I imagine they'll try and dodge the blame. Does this sound like an issue from a neutral point of view? Before my Scirocco I had a 12 year old Mini Cooper and I had similar problems with that, it would always happen though and they had a notoriously bad gearbox so I accepted it but I don't feel like I want to/should with a brand new car!

Thanks in advance

[Gaz r]

Could you get a friend or family member to try it when cold and that would rule out pilot error. If you take it back to the dealer you could leave it with them so they can try it from cold.
When you can't select reverse is it from a standstill or have you moved forward in first and then gone to select reverse, I've had cars where you need to pause for a second before doing so.
Also try a search on the forum for 'gear selector cable damaged' this may be helpful, there is a topic on this that could be relevant.
With it being brand new I would certainly be heading back to the dealer. I'm not sure how the reverse sensors work so as you said it could be down to the retrofit. Good luck mate.