LED rear flashers problem

I'd be interested to hear what the problem is as I have been considering some, but I have heard mixed things about them, people having issues with them.
 
Its due to the extra resistance in the bulbs, you need to replace the flasher relay unit with a special one that allows them to flash properly. Autobulbs direct also sell these.
 
I'v had non canbus and canbus both flash to fast

You can't change the flasher relay according to Renault they said I'd have to put resistors on all four indicators!!!