Hi Nina,
Welcome to the forum, and thanks so much for your report!
We are currently working on Bricks 1.8, which is all about menus with the new Nav Nestable Element and an improved Nav Menu Element. Would you be so kind as to test it again with Bricks 1.8 beta 3 (in the best case, with both menu elements)?
If the problem also occurs, we will try to fix it within the stable release.
You can download the beta version in your account. As with any beta release, please do not use it on any production/live website. It is only meant for testing in a local/staging environment.