I'm currently getting two specific errors in my error log file that are from the Layouts plugin:
[01-Feb-2019 10:04:12 UTC] PHP Warning: array_keys() expects parameter 1 to be array, bool given in /home/mudandroutes/public_html/wp-content/plugins/layouts/extra/buddypress/buddypress.php on line 71
[01-Feb-2019 10:04:12 UTC] PHP Warning: in_array() expects parameter 2 to be array, null given in /home/mudandroutes/public_html/wp-content/plugins/layouts/extra/buddypress/buddypress.php on line 73
[01-Feb-2019 10:06:22 UTC] PHP Warning: array_keys() expects parameter 1 to be array, bool given in /home/mudandroutes/public_html/wp-content/plugins/layouts/extra/buddypress/buddypress.php on line 71
[01-Feb-2019 10:06:22 UTC] PHP Warning: in_array() expects parameter 2 to be array, null given in /home/mudandroutes/public_html/wp-content/plugins/layouts/extra/buddypress/buddypress.php on line 73
While they're not causing any visible issues - i'm currently troubleshooting some intermittent 503s on our site and need to eliminate any possible causes. These errors are in the log every minute or so - depending how busy the site is.
I installed BuddyPress on a site with Layouts and did some basic activity in the backend and frontend and wasn't able to trigger any PHP warnings.
If you can't think of any way on your site where BuddyPress and Layouts are operating on the same pages then I would need a copy of your site to analyse.
As it is multisite it would need something like Duplicator Pro or All in One WP Migration with the multisite extension, do you have access to either of those?
If not I can try to take a copy myself, but I'll need super-admin access.