INSERTS waiting with wait_event is "transactionid"

Hi,
We are trying to load data around 1Bil records into one table with INSERT statements (not able to use COPY command) and they are been waiting for a lock and the wait_event is "transactionid", I didn't find any information in the documents. Queries have been waiting for hours.
Table DDL'sCREATE TABLE test_load(    billg_acct_cid_hash character varying(50) COLLATE pg_catalog."default" NOT NULL,    accs_mthd_cid_hash character varying(50) COLLATE pg_catalog."default" NOT NULL,    soc character varying(10) COLLATE pg_catalog."default" NOT NULL,    soc_desc character varying(100) COLLATE pg_catalog."default",    service_type_cd character varying(10) COLLATE pg_catalog."default",    soc_start_dt date,    soc_end_dt date,    product_eff_dt date,    product_exp_dt date,    curr_ind character varying(1) COLLATE pg_catalog."default",    load_dttm timestamp without time zone NOT NULL,    updt_dttm timestamp without time zone,    md5_chk_sum character varying(100) COLLATE pg_catalog."default",    deld_from_src_ind character(1) COLLATE pg_catalog."default",    orphan_ind character(1) COLLATE pg_catalog."default",    CONSTRAINT test_load_pk PRIMARY KEY (billg_acct_cid_hash, accs_mthd_cid_hash, soc));
query results from pg_locks ;
 SELECT COALESCE(blockingl.relation::regclass::text, blockingl.locktype) AS locked_item,    now() - blockeda.query_start AS waiting_duration,    blockeda.pid AS blocked_pid,    left(blockeda.query,7) AS blocked_query,    blockedl.mode AS blocked_mode,    blockinga.pid AS blocking_pid,    left(blockinga.query,7) AS blocking_query,    blockingl.mode AS blocking_mode   FROM pg_locks blockedl     JOIN pg_stat_activity blockeda ON blockedl.pid = blockeda.pid     JOIN pg_locks blockingl ON (blockingl.transactionid = blockedl.transactionid OR blockingl.relation = blockedl.relation AND blockingl.locktype = blockedl.locktype) AND blockedl.pid <> blockingl.pid     JOIN pg_stat_activity blockinga ON blockingl.pid = blockinga.pid AND blockinga.datid = blockeda.datid  WHERE NOT blockedl.granted   order by blockeda.query_start
"transactionid" "18:20:06.068154" 681216 "INSERT " "ShareLock" 679840 "INSERT " "ExclusiveLock""transactionid" "18:19:05.504781" 679688 "INSERT " "ShareLock" 679856 "INSERT " "ExclusiveLock""transactionid" "18:18:17.30099" 679572 "INSERT " "ShareLock" 679612 "INSERT " "ShareLock""transactionid" "18:18:17.30099" 679572 "INSERT " "ShareLock" 679580 "INSERT " "ShareLock""transactionid" "18:18:17.30099" 679572 "INSERT " "ShareLock" 681108 "INSERT " "ExclusiveLock""transactionid" "18:14:17.969603" 681080 "INSERT " "ShareLock" 681204 "INSERT " "ExclusiveLock""transactionid" "18:13:41.531575" 681112 "INSERT " "ShareLock" 679636 "INSERT " "ExclusiveLock""transactionid" "18:04:16.195069" 679556 "INSERT " "ShareLock" 679776 "INSERT " "ExclusiveLock""transactionid" "17:58:54.284211" 679696 "INSERT " "ShareLock" 678940 "INSERT " "ExclusiveLock""transactionid" "17:57:54.220879" 681144 "INSERT " "ShareLock" 679792 "INSERT " "ExclusiveLock""transactionid" "17:57:28.736147" 679932 "INSERT " "ShareLock" 679696 "INSERT " "ExclusiveLock""transactionid" "17:53:48.701858" 679580 "INSERT " "ShareLock" 679572 "INSERT " "ShareLock"

query results from pg_stat_activity  ;

SELECT pg_stat_activity.pid,    pg_stat_activity.usename, pg_stat_activity.state,    now() - pg_stat_activity.query_start AS runing_time,    LEFT(pg_stat_activity.query,7) ,    pg_stat_activity.wait_event   FROM pg_stat_activity  ORDER BY (now() - pg_stat_activity.query_start) DESC;
|
| | | | | |
| 681216 | postgres | active | 07:32.7 | INSERT  | transactionid |
| 679688 | postgres | active | 06:32.2 | INSERT  | transactionid |
| 679572 | postgres | active | 05:44.0 | INSERT  | transactionid |
| 681080 | postgres | active | 01:44.6 | INSERT  | transactionid |
| 681112 | postgres | active | 01:08.2 | INSERT  | transactionid |
| 679556 | postgres | active | 51:42.9 | INSERT  | transactionid |
| 679696 | postgres | active | 46:20.9 | INSERT  | transactionid |
| 681144 | postgres | active | 45:20.9 | INSERT  | transactionid |
| 679932 | postgres | active | 44:55.4 | INSERT  | transactionid |
| 679580 | postgres | active | 41:15.4 | INSERT  | transactionid |
| 679400 | postgres | active | 39:51.2 | INSERT  | transactionid |
| 679852 | postgres | active | 37:05.3 | INSERT  | transactionid |
| 681188 | postgres | active | 36:23.2 | INSERT  | transactionid |
| 679544 | postgres | active | 35:33.4 | INSERT  | transactionid |
| 675460 | postgres | active | 26:06.8 | INSERT  | transactionid |

select version ();
PostgreSQL 11.6, compiled by Visual C++ build 1800, 64-bit

CPU: v32RAM: 320 GBshared_buffers = 64GB
effective_cache_size = 160 GB

any comments on the issue?

Thanks,Rj