pgBouncer - got packet 'D' from server when not linked WARNING messages

Hi everyone;

We use pgBouncer for pooling, we see like these messages in pgb logs;

WARNING S-0x118b7c0: db/username(at)dbip:port got packet '2' from server when
not linked
WARNING S-0x118b7c0: db/username(at)dbip:port got packet 'T' from server when
not linked
WARNING S-0x118b7c0: db/username(at)dbip:port got packet 'D' from server when
not linked
WARNING S-0x118b7c0: db/username(at)dbip:port got packet 'C' from server when
not linked
WARNING S-0x118b7c0: db/username(at)dbip:port got packet 'Z' from server when
not linked
WARNING S-0x1170a88: db/username(at)dbip:port got packet '1' from server when
not linked
WARNING S-0x1170a88: db/username(at)dbip:port got packet '2' from server when
not linked
WARNING S-0x1170a88: db/username(at)dbip:port got packet 'T' from server when
not linked
WARNING S-0x1170a88: db/username(at)dbip:port got packet 'D' from server when
not linked
WARNING S-0x1170a88: db/username(at)dbip:port got packet 'C' from server when
not linked
WARNING S-0x1170a88: db/username(at)dbip:port got packet 'Z' from server when
not linked

Actually there are different types messages also but we think all of them
independent. one of them is above.

others like these:
- bla bla pooler error: server conn crashed?
- FIXME: query end, but query_start == 0
FIXME: transaction end, but xact_start == 0

and our environment:

PgBouncer 1.17.0
libevent 2.0.21-stable
adns: evdns2
tls: OpenSSL 1.0.2k-fips 26 Jan 2017
mode is transaction
avr TPS = 20K
postgres version 14.5

Have you encountered this problem before, what causes this and what is the
solution?

Thanks in advance...