Message appears when having several WPMUDEV plugins activated at the same time

Hi,

I have recently transferred my site to a new server, and now I receive this error:

"Notice: Indirect modification of overloaded element of WP_Hook has no effect in /.../wp-content/plugins/snapshot/lib/WPMUDEV/Dashboard/wpmudev-dash-notification.php on line 58

Warning: Cannot modify header information - headers already sent by (output started at /.../wp-content/plugins/snapshot/lib/WPMUDEV/Dashboard/wpmudev-dash-notification.php:58) in /.../wp-content/plugins/membership/app/controller/class-ms-controller-plugin.php on line 99"

I have the Membership 2 Pro active, and when I install and activate another plugin like eg. Snapshot Pro, the above message appears.

What could be the problem, and how do I fix this?

I have granted support access to my site if that is needed.

Thanks!