How do I find out what's causing processes to wait for table flush?

I'm currently using MariaDB 10.3 and am troubleshooting this case where threads will start to build up until the MySQL service eventually has to be restarted. I was able to capture the process list before restarting MySQL, but I have a few questions that I hope will help me head in the right direction. In the screenshot below, I've included a portion of the process list, which I sorted by time. The same thing has happened two different days, and on both days, the output is very similar. From looking at the processes, there are two things I've observed: 1. There is a longer running process in the statistics state. 2. All of the processes are waiting for the table flush after our database backup process, which seems to be waiting for a table flush itself. I need to confirm with the team what tool is being used for backups, but I believe it might be something from Percona. The main issue I'm trying to solve here is figuring out what's causing all of these processes to wait for a table flush, but I'd also like to understand the output here. Does this output produce something that looks obvious in terms of what's causing it or is there a particular way you would go about figuring this out? Thanks in advance!