Suitecrm getting slow randomly

Hello Team,
I’m having issue with Suitecrm getting very slow randomly. and in backtrace we are getting below query error. is anyone know why this issue and error getting.

Error 1:
Message:Call to a member function isCollection() on bool
Exception:PHP Fatal error
select reminders.* , jt0.user_name modified_by_name , jt0.created_by modified_by_name_owner , N’Users’ modified_by_name_mod , jt1.user_name created_by_name , jt1.created_by created_by_name_owner , N’Users’ created_by_name_mod , jt2.user_name assigned_user_name , jt2.created_by assigned_user_name_owner , N’Users’ assigned_user_name_mod from reminders left join users jt0 on and jt0.deleted=‘’ and jt0.deleted='’ left join users jt1 on and jt1.deleted=‘’ and jt1.deleted='’ left join users jt2 on and jt2.deleted=‘’ and jt2.deleted='’ where (reminders.related_event_module = N’’ and reminders.related_event_module_id = '’) and reminders.deleted=’*****'Executions2

Error 2:

Message:Trying to get property ‘_instance_properties’ of non-object
Query 2:
select id , as sub_department_c , securitygroups.assigned_user_id owner from securitygroups where deleted=‘’ and id=N’

Can you provide evidence on the speed problem - you say it goes slowly - but have you graphs/timings from the past and from now?

Or other data on what ‘very slow’ means in numbers.
And if it is randomly - when does it occur - in office-hours only or 24/7 ?