I went with MPSS 305 square in my 2017 GT350, original non-R wheels, and have been very pleased. What little tramling there was with the factory 295/305 is completely gone with the square setup.
I agree with @Cobra Jet, it's cracked seam sealer. Personally I would take a small pick and poke around a little, should be fairly easy to determine if it is sealer, or not. I'd be very surprised if it isn't...
Happened 3-4 times with my 2017, mostly when it was new, nothing unusual. This shifter can "trick" you into thinking it's all the way in 1st when it's not. I just adapted by always shoving it firmly into 1st gear, then removing my hand from the shift knob before letting the clutch out to prevent...
In case anyone is interested...
Saw this today at Bickford Ford, Snohomish, WA, while picking up a part for my GT350. Sales person said ~$109K and they also had a second GT500 (non-CFTP) with 8700 miles for ~$91K. Believe both are now listed on their website.
It would be interesting to know how much involvement SAI had in developing the current GT350, I would suspect minimal at best. Guess I'm just an old school purist, as far as I'm concerned SAI's involvement with the GT350 and GT500 ended during the 1967 model year when Ford took over production.
^^ This.
I bought the Gorilla 61148CX for my 2017 several years ago from CJ Pony Parts but it looks like they don't stock them anymore. Summit carries them, https://www.summitracing.com/parts/gor-61148cx, and also saw some on ebay.