What is as important is that you require the insurance to be issued with you as the landlord as "additionally insured." 

Over months of working with her, I encountered severe issues, including:Lack of Communication & Accountability – Corina ignored multiple emails for weeks or even months, providing misleading or vague responses instead of real updates.

Working on large-scale data is great b/c sometimes it's all about how many owners you approach daily; the issue with over-the-top details is also getting lost in targeting specific owners and situations, aka focusers/tax liens, etc.

And that is the issue. 

I understand this is not a requirement, but I have never received a damaged unit from an inherited tenant or any legal issues.

And also that rates are just going to continue to be an issue, so it's likely something to plan for in rent rates and/or overall investment costs. 

The quality of tenants could be an issue.   

Can anyone recommend good companies to root cause  and implement solution to fix this issue?

Can you explain how your company solves the partial note issue? 

Assuming they are professional and skilled in the craft - alot of the issues you have faced, they will remediate and mitigate moving forward.