Defender "server resource usage is too close to your limit."

Hello!
I am getting the "server resources usage is too close to your limit" error when running a scan. I found this thread
https://premium.wpmudev.org/forums/topic/defender-server-resource-usage-is-too-close-to-your-limit-mu-plugin-code#post-1151129
& added the mu plugin, but it has not solved the problem.
I have granted support access.
Thanks for your help!
Debbie