Plastic hotbed shroud shifting

When my print bed heats up, the shroud covering the sides and bottom of the bed, deforms with an clearly audible snap. First the front left edge snaps down a mm or 2, some time later the right edge follows.

Clearly some tension is building up here.

Is this a common thing? is it a problem? Is there a fix?

Yep, that’s unfortunately normal. It only affects the plastic trim and nothing print related, I didn’t notice any negative effects on the print.

I use it as an audible indicator that the print bed has reached 60°C…

And here is also a related Wiki guide: