Just register the amount of /fix per user, then, when the amount is higher than normal players, check out what they are actually doing wrong... as a normal online player would use it about once an hour. (depending on the favorite road they take.. ) And if they show wreckless driving, endangering others or something else that makes them use /fix more, give 'm the boot for a couple of days to think about their sins.
The /Fix is "the" best option you couldhave given to get our truck to the destination. No need to say sorry, for coming up with a solution for a "human"-problem.
Woof ~ Woof & Salute!