Mongodb performance issue in 7.0

Hi Team,
we are finding slowness/inconsistency in write speed on mongodb 7.0
On 7.0.4 installation with 6.0 feature set and we are able to injest 250mn events an hour (batch size 100 events) with avg latency of 100microsecs per event. Once we switch to 7.0.4 feature set, the avg latency turns out to 500 microseconds per event and eventually increases more than 1000 microseconds. Sometimes it increases and decreases and shows inconsistency in write speed. After writing few milion events, if we switch again to 6.0 feature set, the write avg latency switch back to 100 microseconds per event and it stays consistent even after billions of events injestion. We observed the same with 6.0 installation too not just with 7.0.4 installation with 6.0 feature set.

Create collection query:
db.createCollection(“weather”,{timeseries:{timeField:“time”, metaField:“meta”,granularity:“hours”}})

we do insert many query

mongo is installed with 7.0.4 version
command used for switching feature set:
db.adminCommand( { setFeatureCompatibilityVersion: “7.0”, confirm: true } )
db.adminCommand( { setFeatureCompatibilityVersion: “6.0”, confirm: true } )

command used for checking feature set:
db.adminCommand( { getParameter: 1, featureCompatibilityVersion: 1 } )