Do you experience this loss of performance in this specific monolith or in all monolith zones? The one you recorded a massive spike is known to have some issues.
I asked the question above because this particular zone has had issues before. I know you are having performance drops in general but I would like to know if you are getting the same degree of performance drops in other monolith echoes. This information will help determine if the performance drop is linked to Multishot or zone related.