Irregular DB response time if Haproxy statefullset is greater than 1

Hello all thanks in advance for your help, I am testing one of our applications with a Percona XtraDB Cluster (PXC) Version 1.16.1 (mysql 8.0.39)
The installation was carried out with a default configuration of 3 PXC and 3 haproxy. The application is responsive, and performance is good except on one page of the Typo3 application (which is a content manager)
The refresh time of this page is either 2.5 seconds or 12.5 seconds. (for the refresh of this page more than 3000 sql Statements are performed)

If I connect the application directly to the primary DB the response time is constant (2.5 Sec) and if I set the Statefullset of haproxy to 1 the response time is also constant (2.5 Sec)

Haproxy’s metrics seem correct to me, and I didn’t find anything in the logs.

Any idea why this behavior?