High CPU usage

I installed version 1.9.0 of the elastic APM agent into production server which runs php-7.4 on ubuntu 20.04 .
The application itself is a large mysql backed Zend(1.1) application.

After installing APM withing few hours CPU is usage over 95% and application got crashed

After disabling the APM it returned to very low CPU usage and everything works fine

Congifuration:-

elastic_apm.enabled = true
elastic_apm.environment = "production"
elastic_apm.server_timeout = "30s"
elastic_apm.async_backend_command = true
elastic_apm.transaction_max_spans = 500
elastic_apm.transaction_sample_rate = 1.0