inserts take longer and longer

hi all.

I hope this is the correct way to get help from the list.

we are postgres 10.4 :
# DB Version: 10
# OS Type: linux
# DB Type: mixed
# Total Memory (RAM): 60 GB
# CPUs num: 22
# Connections num: 100
# Data Storage: san

we have a developer who is doing
batch inserts 20 at a time and each subsequent batch is taking
longer to the point where it is a critical problem. I recently changed
the out of the box config to see if that would help but it hasn’t:

max_connections = 100
shared_buffers = 15GB
effective_cache_size = 45GB
maintenance_work_mem = 2GB
checkpoint_completion_target = 0.9
wal_buffers = 16MB
default_statistics_target = 100
random_page_cost = 1.1
effective_io_concurrency = 300
work_mem = 7149kB
min_wal_size = 1GB
max_wal_size = 2GB
max_worker_processes = 22
max_parallel_workers_per_gather = 11
max_parallel_workers = 22

any direction as to what to look at would be appreciated.

david