"We have confirmed an issue wherein cars in your garage can disappear if you are playing 'Gran Turismo Sport' with the same PlayStation™Network account on more than one PlayStation®4 system.
This issue can occur if you install Update 1.19 on one PlayStation®4 system, then use the same PlayStation™Network account on a different system where Update 1.19 is not installed.
We are planning to fix this issue with the next update. Until then, if you are currently playing 'Gran Turismo Sport' on multiple systems, please refrain from using the same PlayStation™Network account when using the other systems.
We sincerely apologise for the inconvenience this may cause, and thank you for your understanding."
https://www.gran-turismo.com/ru/gtsport/news/00_8350873.html