Incompatibility?: Multisite and Ultimate member – User reviews

I’m building a multisite. I’m considering purchasing Ultimate Member – User Reviews 1.1.6 but some colleagues of mine have advised me not to. They said that when you installed User Reviews on a multisite it crushed both the WordPress plugin search and the plugin “UpdraftPlus – Backup/Restore 2.12.30.1” (last version).

– WordPress plugin search: If you go to “My Sites” => “Network admin” => “Plugins” => “Add new” => Text field “Search plugins…” => If you search anything, the search does never end and doesn’t show any results at all.
– UpdraftPlus – Backup/Restore 2.12.30.1: If you go to “My Sites” => “Network admin” =>”Settings” => “UpdraftPlus Backups” => “Existing backups” (tab) => <<Warning: Your WordPress installation has a problem with outputting extra whitespace. This can corrupt backups that you download from here>>.

Apparently if you deactivate User Reviews both bugs/errors disappeared.

Is there a known incompatibility between User Reviews and a Multisite installation?
If it isn’t, could you tell us how to avoid those problems.

Thank you so much for your effort and time.