Don’t park your car in any garage. This is the warning coming from Rockstar after a pretty crappy bug has emerged.
Rockstar says they are looking into a teeny tiny glitch that only sometimes causes cars to completely lose upgrades or vannish from the safe house. Awesome. 
A support forum shows the developers saying they are “looking into” the problem.
“Unfortunately, we do not currently have a workaround to recover a car if it is missing,” they added.
Trevor, Franklin and Michael The main characters in GTA V are Trevor (left), Franklin and Michael (right)
“In the meantime, please try to avoid parking a car in a garage, driving one already in a garage, or getting in a default vehicle, when playing as a character other than the one with your upgrades.”
Rockstar suggested the issue may occur if players drive different characters’ personal vehicles.
Grand Theft Auto V
They added: “Also please note that vehicles saves in the garage of one safe house (Franklin’s Aunt’s) may not show up in the garage of a different safe house (Franklin’s Vinewood Hills).”
Rockstar suggested players should subscribe to their support site feed for automatic updates on the issue.