How many miles on the car?
In The Olden Days, new Guibos were supplied with a steel strap around them. Don't know if that's still true, but, if it is, leave the strap on until all bolts are tight. The strap serves to compress the rubber in order to get the bolts in.
When the nuts are nearly tight do not turn the bolts, but just the nuts. This will prevent twisting the steel inserts.
Ed in San Jose '97 540i 6 speed aspensilber over aubergine leather. Build date 3/97. Golden Gate Chapter BMW CCA Nr 62319.