@ OP but anyone else really.
Not sure if relevant either but it's to do with the DSG so maybe it might strike some conversation.
ST300
Cupra 4Drive late-18 build, meaning GPF and DSG7 box.
So this has happened twice so far, and I haven't tried to replicate the situation for fear of ruining my poor car. It happens during a warm start, usually the second time I've driven the car for the day - meaning that it's still warm from when I have driven to school/shops/whatever maybe water temp at 80*~.
Outside my apartment block there is a real nice long stretch of road (toward the town) that if one was bored and wanted to do a rapid acceleration for fun (10kph to 80kph, y'know to try to get the DSG to burp - upshift 1st into 2nd, maybe into 3rd), they could. So what has happened in these two instances is that when I am upshifting from 1st into 2nd gear (hard acceleration [not kick-down though], shifting manually at 5500-6000rpm maybe higher) I would hear this LOUD clank - like a piece of metal hitting a plastic box really hard - and simultaneously lose all power for about 2 seconds before 2nd is engaged and all is well again.
My theory is that the clutch "slips" and disengages before trying to re-engage 2nd gear. Maybe it's because I'm asking the car too soon to get a move on - because the first time it happened, I immediately tried to recreate the situation and it shifted normally (so it's always the FIRST time it has to shift from 1st to 2nd, i.e. out from the carpark or whatever).
I haven't had my first service yet, and I'm unsure if its a thing I should get checked because it only happens in that situation.
In addition, my two cents on the 'traffic crawl' (i.e. slow speed driving) situation - I always avoid manual mode (to lock it in 1st for example) because it's way too jerky - and generally I let it get into a situation where it can crawl (so its not having to work the clutch). But if I am in a carpark, and I have to go up ramps or whatnot, yeah then I engage manual mode to lock it in 1st so it's always on power and not always stupidly shifting to 2nd or even 3rd.