i have banned account with 3 drivers all lvl 50, & another one i use boost in it, didn't got banned
& i knew somebody buy boost like a CRAZY & he got all boost cars with all boost bodykits & &....guess what..., he is banned
all i can say it's random, u can do some good things like have boost cars & to have normal TH day streak & don't let others report u...
another idea is...banning comes after the reason by some days, if the account wasn't banned....it will not be banned in future
Have fun.