[system test] Indexing is slow/stuck after KV-Rebalance in/out and Index Rebalance Out on cluster

Drain rate on Index node is about 60-80

Mutations ( select, insert, update, delete) is about 2-3k

Indexing for the past 1 hour is very slow and the drain rate is slow compared to incoming mutations.

This cluster seemed shows this behaviour today and has been running w/ steady state ( no cluster topology changes) for the past 2 days.

attached screenshot, adding logs.