Complete loss of fuel pressure after spirited driving

[ZoliWorks]

Long story short, if I drive the car spiritedly, then stop, in just an hour, the rail pressure disappears completely. When I un-do the valve on the HPFP, nothing comes out. Alternatively, even if I drive normally, if left sitting for a day, the same happens.
When I try to cold start the car, not only does it crank a few times before starting, but it also makes a noise as if the whole system is filled with air when I open the door and the electric pump kicks in.

Current setup:

• Stock k03 injectors
• Stock LPFP
• RS4 FPRV
• Vis Motorsport HPFP Internals on stock lpfp

The car has been having this issue since I've bought it. The colder it is outside, the more likely it is to crank more before it starts up.

Thoughts on what it could be? leaky injectors, bad hpfp or failing lpfp one way valve?

Attached video, watch on max volume when I open the door.


EDIT: To add some more info, lpfp pressure almost never drops below 5 bar. Fuel filter is 6.6 bar, replaced 20k km ago. HPFP has no issues maintaining 130 bar at full throttle throughout the rpm range, pump has vis motorsport internals done a few months ago, cam follower was done 20k km ago and last I checked, when doing the hpfp, it was still good. Just a tiny dot in the middle, no uneven pattern.

[mjmallia]

Sounds like the LPFP to me. There is a flow back valve in the unit that with age starts to bleed fuel and not keep pressure, creating starting problems and could explain the lack of fuel in the HPFP after sitting a bit.  This valve is there to keep that pressure against the HPFP for a quick start.

LPFP life expectancy is about 100k miles......looking at replacing mine for peace of mind as refreshing the old girls parts as you know.

[ZoliWorks]

Funny thing, forgot to mention. After turning the car off and letting it sit, I can hear droplets noise coming from the fuel tank, as if fuel would be trickling back. Mostly notable after medium to hard driving. My money is on the pump being the culprit cause I've heard it having issues. Been meaning to replace it since half a year ago but always found something more "important" to do 

I'll be replacing the LPFP next month anyway with a new, complete unit, along with the N80 evap valve, the evap canister and the rubber line linking the evap canister to the metal low pressure fuel line coming out of the hpfp and the FPRV.