I am running Events Manager 5.5.7 and Events Manager Pro 2.3.9. This is a multi-site install.
If it helps, I took a look at the code and found where the error was being thrown. When I look in admin/em-bookings.php at the em_bookings_event() function (line 86-141), it seems like the logic requires the user to have BOTH manage_bookings and manage_others_bookings.
if( is_object($EM_Event) && !$EM_Event->can_manage('manage_bookings','manage_others_bookings') ){
There doesn’t seem to be any logic there to check (if the user has manage_bookings and is the owner/author of this particular event).
HTH!