PostgreSQL exporter throws "queryNamespaceMappings returned N errors"

One of the recently onboarded MS PG customer reported an issue that PostgreSQL exporter throws an error:

Feb 17 03:27:50 gmsql11-p2lg pmm-agent: #033[31mERRO#033[0m[2023-02-17T03:27:50.502+00:00] ts=2023-02-17T03:27:50.502Z caller=postgres_exporter.go:742 level=error err="queryNamespaceMappings returned 1 errors"  #033[31magentID#033[0m=/agent_id/7cf7ec5b-b499-4871-961f-cb9aafb6c6f4 #033[31mcomponent#033[0m=agent-process #033[31mtype#033[0m=postgres_exporter 

I was able to reproduce the issue on 2.29.1 with RDS PostgreSQL 13.7, but not on 2.34.0. 

Customer's setup:

• PMM Server version: 2.34.0
• PMM Client version: 2.34.0
• PostgreSQL version: PostgreSQL 12.3 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-39), 64-bit

Additional info from customer:

• PostgreSQL running on a Physical server
• PostgreSQL service was added using platform automation script
• There are total 6 DB Instance having 3 different environments (master-replica set up) - out of which 2 instances of single environment have this issue
• Link to Slack thread: https://perconacorp.slack.com/archives/C03FB1CAZH9/p1676264835439279