For what it's worth, as an auto tech we are limited in what we can do. For a vast majority of car makes, we have no access to anything that happens on the back-end of the control modules. We can look at some data stream on a scan tool, but that is limited at best. There is no debug access or anything of that nature. It's also well outside the skillset of most technicians to delve into software. Also, If you look into the pay plan of most dealer technicians, (flat rate/paid per job) then you understand why we don't want to spend all day looking at your turn signal. We won't get paid for most of the diagnosis time.

If you’re in the US, report it to the NHTSA:

https://www.nhtsa.gov/report-a-safety-problem#index

Wow, the jerking also? That is enough for a recall, or should be!

If you are in the EU, have you spoken to the consumer ombudsman (or whatever name it has)?