ERROR: invalid message format and FATAL: invalid frontend message type XX logs

[fatih abztn <fatihabztn@xxxxxxxxx>]

Hi;

    We're seeing  lots of  errors  in postgres server logs, we have no idea about them.  Especially  under higher load, it seems to happen more frequently.  There are thousands:

 ERROR:  invalid message format

 FATAL:  invalid frontend message type 0 

 FATAL:  invalid frontend message type  32

 FATAL:  invalid frontend message type  101

 FATAL:  invalid frontend message type  34

 FATAL:  invalid frontend message type XX

.....

  What does it mean and  how to solve this problem?  

and our environment:

npgsql -> pgBouncer 1.17 ( in transaction mode )-> pg14.4

I am waiting for your comments...