How unusual/newsworthy is a NTSB investigation? You can look at their list of major highway investigations right here:
https://www.ntsb.gov/investigations/Pages/All-Investigations...
There are about 50 ongoing investigations since 2016. Of those, Tesla is the subject of 4 of them:
https://www.ntsb.gov/investigations/pages/HWY18FH004.aspx
https://www.ntsb.gov/investigations/pages/HWY18FH011.aspx
https://www.ntsb.gov/investigations/pages/HWY18FH013.aspx
https://www.ntsb.gov/investigations/pages/HWY17FH013.aspx
By my informal count, Tesla seems to have the most NTSB investigations of any individual automaker right now, given that many of the NTSB highway investigations involve bus and train accidents.