First, in my organized races, I won't even allow the race to proceed until everyone's invisible car problems are solved.
I build in 15-20 minutes into the schedule, before qualifying for dealing with VISION CHECK - and solving the problem.
Because sometimes it doesn't happen - but when it does, it can take 20 minutes + to deal with it & solve the problem.
OFTEN, if someone can't see another car, that driver can't see their car either. BUT, that's not always the case.
OFTEN, it's the same people who have problems with certain other people. BUT, that's not always the case.
OFTEN, it's happening usually to people using WIRELESS connection instead of a cat6 network cable to connect from the router to the ps3. But that's not always the case. AND, those same people don't always have the problems. (Often it's the mix of certain players together with their various connection issues.)
CURES & PROBLEM SOLUTION:
Sometimes those having the problem, switching to a hard wire cat6 network cable, and then re-entering the lounge, will solve the problem for ALL parties involved.
Sometimes just those having the problem leaving, clearing cache, and returning, will solve the problem.
Sometimes, everyone leaving and returning, after rebooting gt5, or the entire ps3, will solve the problem.
The ONLY cure that works 100% of the time that I've tried is to switch to a public lobby room, with FIXED HOST STATUS.
It is the ONLY way to solve the problem 100%, for everyone, especially those with multiple connection issues. (IE: other people at their house using the internet, inability to hook up a hard wire cat6 cable connection, or maybe if they're just clueless as to how to reboot the game their ps3 and clear the cache - I don't know.)
So if you're having persistent problems with this, and the minor fixes (like leaving, clearing cache, etc.) do NOT work. Then there's only 3 options:
1.) You switch to pub lobby with fixed host status
2.) You ban those who have the problem & can't solve it on their own
3.) You race with invisible cars
Option 2 is rather lousy for obvious reasons.
Option 3 is UNACCEPTABLE to me, as it makes stewardship of races IMPOSSIBLE... if people can just claim the car they punted was invisible to them, for example.
Anyway, also, WSCC members have told me that in their experience, the HOST of the lounge having a crappy connection, or not having recently rebooted their machine, or not having recently cleared their cache, etc... can have a dramatic effect on everyone else's visibility issues - REGARDLESS OF WHETHER OR NOT THE HOST HIMSELF/HERSELF is having visibility issues.
In other words, a host with a slow connection or a plugged up cache, or a wireless connection, can not have invisible cars, not be experiencing the problem from their point of view - but can cause other participants in the room to have invisible cars.
Is this the case? Several people have told me they firmly believe that this is the case.