I have a new Thule double bike rack on a newly fitted swing out towball arm, which is attached to my new Adria Twin (Fiat Ducato). all very nice I know. . problem is, the bikes (and rack) seem to bounce alarmingly over small bumps in the road and even worse on speed bumps. Has anyone else experienced this? So far the manufacturer has directed me to the dealer who has sent me back to the installer. Before I start the whole process off, I just wondered if anyone else have had this issue? The bikes are within the weight tolerance BTW