Free burning software often has small bugs, could be some timeout or a misinterpretation of a 2part SCSI message etc. With ASPI it was fairly trivial to diagnose these issues, used to just load a dummy WNASPI32.DLL that logs traffic into a text file, but it’s a little more complicated getting useful info hooking SPTI and related functions.
I wouldn’t describe your results so far as having “excellent burning qualities” - merely they are “fine”, ie. good enough for MOST purposes, not edge cases like picky readers.
Since you are dealing with a car system, those are definitely known to be particularly picky about what media they accept. Your scans posted so far have shown a high level of PIEs and high jitter, not to mention the POFs, so you’re probably gonna have to improve on that. The main difference between a pressed disc and a burned one is the reflectivity and jitter (which is perfect on a pressed DVD, chaotic on burned discs). Since you’re already using MIDs with good reflectivity and other design characteristics as well as a decent burner, the only further improvement is to obtain better quality media, such as TYG02 from 2005-2006, MCC 004 from 2005-2007 made by CMC Magnetics on the PAPA manufacturing line, or certain batches of MIJ MAXELL MIDs. Anything else is a gamble, an invitation to waste even more money.
Of course DVD+R DL is a no-go, since that is a very finicky media even under the best conditions (the 2nd layer has extremely low reflectivity, nearly unreadable on players that don’t adjust the laser power automatically).
I can give further guidance or even offer some of my own media (I have a lot of 2007 MCC 004, with PAPA serials) but I don’t know if you have the will to fiddle with it further? I suppose if the problems are intermittent, then you could get away using the discs you have, making several burns and so on.
I don’t use navigation systems, I choose to rely on old fashioned paper maps so I can’t give you any specific guidance on that topic. But usually standalone DVD readers have a potentiometer inside that controls laser power, adjusting that could potentially make it a more reliable reader for burned media IF the problem is reflectivity, but it won’t make a difference if the cause is poor error correction circuitry.
PS. I am the author of CD2Date, a software that helps determine the month, day and year that a particular disc was manufactured, which may be of help to you if you do plan on finding the media I mentioned, you can find the download link and instructions here.