Reverse to first clinking noise ??

I wonder has anyone cross this problem ?

When I reverse and to into first gear I hear clinking noise like something is trying to pull the car back ?

The garage can find no fault, when it occurs its very loud.

Is it while youre moving? weve had a lot of people with a strange crunching sound like driving over a plastic bottle just as pulling away after reverse, had it myself, but no idea what it is, probably brake related to one of the systems hence the feeling of being pulled back, but doesnt seem to be an issue fortunately.