3d print bed rocks back and forth

Been using my A350 for over a year with mostly the 3d printing.
I’ve noticed more lately a rocking of the print bed when printing items that are a little taller although it rocks for all prints actually.
My concern is the higher it gets the more likely it will knock the piece over because of this rocking.
What is the cause because this is making it useless for printing larger pieces.
What good is the larger print area if I cannot actually use that size successfully?
Please advise.

I’d double check all the screws are in place.
I haven’t had mine long, and then noticed a couple of screws sitting under the bed. Then realised that these are the ones that secure the base to the linear drives.

This is a known issue. If you’re really having severe problems, additional passive rails underneath the bed can help ( Minimize rocking has a recipe, although you’ll have to read much of the thread to collect the necessary details).