Well, I've unfortunately experienced this lack of FFB issue myself. I have little to inform as it was unexpected, but I'll give the best description I can.
To start (my signature includes my devices), I was in career mode and had just finished a 25% race at Baku in the McLaren. I used a custom setup and had great FFB through the entire race weekend (3 practice sessions, knock out qually, 25% race). Moved on to Spanish GP, still in career mode. Loaded a custom setup from the setup forum and started with Track Acclimatization in P1. Track felt green, especially on hard tires, but normal as far as FFB is concerned. Finished Track Acc., making a few small setup changes along the way, and moved on to the Fuel Management program.
This is where things got weird. Pulled out of the pits and the FFB felt extremely different. Like a switch got flipped. It was like somebody else described, like there were snowmobile skis replacing the front tires (maybe a bit of an exaggeration, but that's definitely the FFB sensation compared to normal). I switched from hard to medium tires and while the grip level changed as one would expect, it was relative to to overall reduced FFB. Still like having snowmobile skis, but now with fresh carbides installed. I couldn't come within 1 second of hitting my target fuel management time, and I know Barcelona very well from years of racing it on other sims. Numb, weak, low resistance (like power steering), and non-dynamic is how I would describe the FFB. It really felt like the car's front tires weren't making full contact with the track surface. This had me pushing hard as I could, but just couldn't make solid lap times. This, despite hitting brake points, apexes, using runoff curbs, and running what I consider clean laps. Tried resetting/reloading my setup, then tried unmodified setups, and everything felt pretty much the same, except for expected changes in understeer and oversteer.
Frustrated, but not wanting to quit racing for the evening, I decided to restart my F2 career. Pulling out of the pits at Bahrain I was SHOCKED at how much different the wheel felt. My wheel was "switched back on." I had a lot more turning resistance, the front wheels felt connected to the track surface, small inputs had a greater impact (what I consider that "dynamic" feeling), and the car was responding to those inputs how I expected it to. In short, I was relieved there's still a playable part of the game while the devs try to figure out what's causing this FFB issue in the F1 cars.
Since this was my first negative experience with the game I wasn't really in troubleshooting mode, so I didn't do any further testing. But I'll definitely follow the guidelines set forth by @Hoo in any future sessions and report back on the results. I also noticed an error code just before shutting down the game, but unfortunately have no idea when the error occurred. I'm still including the code at the bottom of the post. Hopefully this is a correctable bug. I know troubleshooting random faults is the most difficult kind of troubleshooting, but this one is a major bummer and kind of game ruining. I'll do my best to report any additional issues I encounter, and will try to be more detailed in what steps I take to try and isolate when I experience the issue. Thank you for your continued help to the community for testing and reporting, and to Codies for listening and working on fixing the problems we encounter.
Error code: VTMA-MCXS-AASS-PEKG