Performance degradation when running load tests

[dogruis]

I have a service that is using saaj-impl 1.5.3 on Java 11 (G1GC).
When the library has to parse big XML it is not performing well during our load tests.
The parsin can take up to +40s to process a big XML.
The performance degradation doesn't occur when running on Java 8 (ParNewGC) and most of the requests processing time is bellow 1200 ms.

  <dependency>
      <groupId>jakarta.annotation</groupId>
      <artifactId>jakarta.annotation-api</artifactId>
      <version>1.3.5</version>
  </dependency>
  <dependency>
      <groupId>jakarta.activation</groupId>
      <artifactId>jakarta.activation-api</artifactId>
      <version>1.2.2</version>
  </dependency>
  <dependency>
      <groupId>jakarta.xml.soap</groupId>
      <artifactId>jakarta.xml.soap-api</artifactId>
      <version>1.4.2</version>
  </dependency>
  <dependency>
      <groupId>jakarta.xml.bind</groupId>
      <artifactId>jakarta.xml.bind-api</artifactId>
      <version>2.3.2</version>
  </dependency>
  <dependency>
      <groupId>com.sun.xml.messaging.saaj</groupId>
      <artifactId>saaj-impl</artifactId>
      <version>1.5.3</version>
      <exclusions>
          <exclusion>
              <groupId>javax.xml.soap</groupId>
              <artifactId>javax.xml.soap-api</artifactId>
          </exclusion>
      </exclusions>
  </dependency>
  <dependency>
      <groupId>com.sun.xml.bind</groupId>
      <artifactId>jaxb-impl</artifactId>
      <version>2.3.5</version>
  </dependency>