The best way to fix this without wasting cash is targeting the valves. In my experience, if you swapped the bag and it still drops, its usually the residual pressure holding valve on top of the strut. Chicago salt kills them...

• Swap the Audi 4H0951253A Suspension Relay now or youll fry the compressor.
• Inspect the Arnott VB-3267 Air Suspension Solenoid Valve Block. Those VCDS codes usually just mean the system timed out cuz of a leak.

Ngl, that Chicago cold is probably your biggest enemy right now. If your compressor is already groaning, you gotta be careful because it's likely on its last legs. Since you already swapped the bag and the valve block was mentioned by others, you might want to consider moisture in the system as the culprit. Here are a few routes depending on how much you want to spend:

• Rebuild the pump: Bagpipingandy Audi Q7 Compressor Piston Ring Seal Kit. This is the way to go if you want to save cash. It replaces the internal seal that wears down over time. Just be warned, if the cylinder is scratched up inside from debris, it wont last long.
• Replace the whole unit: Arnott P-2539 Air Suspension Compressor. Going this route is much safer for a long Florida road trip. It is way more reliable than a rebuilt unit and usually comes with a new dryer. It is significantly cheaper than the OEM part from the dealer.
• Desiccant beads: I would suggest getting some Dry & Dry Orange Indicating Silica Gel Desiccant and swapping out the old stuff in your dryer. Honestly, if there is water in the lines, it freezes and acts like a plug. That usually throws that vague mechanical failure code on VCDS. Definitely search the AudiWorld forums... there is a massive DIY thread on the 4L Q7 air suspension that explains how to bake the moisture out of the system. It might save your bank account before you head south.

Like someone mentioned, these systems are a total headache in the rust belt. Honestly, I am super satisfied with my Q7 now that it's finally dialed in, but man, it took some serious trial and error to get there without spending a fortune. You gotta be really careful about the ride height sensors... specifically those little plastic linkage arms. In the Chicago winter, road salt gets in there and they just seize up or snap. If the car thinks that corner is already high, it wont fill it properly, making it look like a leak when it's actually a sensor error. Here are a few things I would definitely check before you head down to Florida:

• Check the level sensor wiring harness for green crusty corrosion.
• Make sure the sensor arms actually move freely and havent popped off.
• Recalibrate the system after any component swap or it might stay wonky. Ngl, my biggest worry for you is that compressor. If it's already straining, it's pushing a ton of heat into the lines. I am always cautious about driving long distances with a struggling pump because if it fails on the highway, you're basically riding on the bump stops. That's super sketchy at 70mph and honestly pretty dangerous. Just double check the wiring to that rear left corner... sometimes it's just a frayed wire making the sensor go haywire and confused. No complaints with mine since I fixed the harness, it works well now.