For those still having problems
playing in PC in spite of the suggested fixes above and are willing to go the mod route, try this as this worked for me.
First download this mod:
Cyber Engine Tweaks and follow install instructions in the description of the mod
Then download this mod:
Teleport Fwd, specifically the Teleport FWD - 567 (binds) mod. Follow install instructions in the description of the mod.
This will let you teleport a good distance when you press 6.
Next, when you are done talking to Panam about the plan, let her get inside her vehicle first. You will see the vehicle sink to the ground (this is probably what is causing the problem), then the tires should pop back up from the ground.
When you see the tires pop up from the ground, that should be your cue to make it to the passenger seat.
This part is important: AS YOU ARE ABOUT TO SIT DOWN IN THE PASSENGER SEAT (NOT WHEN YOU ARE CLIMBING UP TO OPEN THE PASSENGER SIDE DOOR) SPAM PRESSING 6 TO TELEPORT YOU FORWARD AND OUTSIDE THE GARAGE. Keep on spamming 6 until you hear V ask "Who owns this power station? Gov or corp?" (NO LOADING SCREEN WILL SHOW; If there is a loading screen, it should be faster now, but stiil, SPAM 6!), that is when you can just sit back and enjoy the ride. NOTE: If you stopped spamming 6 before V asks that question, it will cause the same loading bug screen.
No need to do side quests, main quests, or fast travel. It takes a bit of practice to get the timing right, but as long as you spam press 6 when V is about to sit in the passenger seat, should work. It really isn't hard to time it anyway.
It seems when the vehicle first sank, it was holding it in place and not making the vehicle go forward may be the one causing the bug. But having to force the vehicle out of the garage seems to "unlock" it.
This is by far the most consistent workaround with all the other save files I was testing this on.
Hope it also works for those still having problems.
If you need more info or further help, just hit me up. Always happy to help. Sadly,
this is only for PC users, because we can use the Teleport Fwd mod...