Laminas error in custom server provisioning module

[heapmaster]

We have a custom module that is for plesk that is based off the github (https://github.com/plesk/whmcs-plugin) one that is no longer supported. We use this since have to customize the module so that during service setup it calls our other systems to setup dns and email, which is not hosted in plesk. Since upgrading to WHMCS 8.0.x we are now getting the error in the client area when clicking on the service that uses this module.
Laminas\HttpHandlerRunner\Exception\EmitterException: Output has been emitted previously; cannot emit response in /var/www/vhtdocs/site/html/vendor/laminas/laminas-httphandlerrunner/src/Exception/EmitterException.php:24
Stack trace:
#0 /var/www/vhtdocs/site/html/vendor/laminas/laminas-httphandlerrunner/src/Emitter/SapiEmitterTrait.php(40): Laminas\HttpHandlerRunner\Exception\EmitterException::forOutputSent()
#1 /var/www/vhtdocs/site/html/vendor/laminas/laminas-httphandlerrunner/src/Emitter/SapiEmitter.php(27): Laminas\HttpHandlerRunner\Emitter\SapiEmitter->assertNoPreviousOutput()
#2 /var/www/vhtdocs/site/html/clientarea.php(0): Laminas\HttpHandlerRunner\Emitter\SapiEmitter->emit(Object(WHMCS\ClientArea))
#3 {main}

How can we fix it and why is it doing this. The lib folder in our custom module folder is copied from the modules/servers/plesk folder that WHMCS provides.

Edited October 8, 2020 by heapmaster

[heapmaster]

I even use the default example (from here https://raw.githubusercontent.com/WHMCS/sample-provisioning-module/master/modules/servers/provisioningmodule/provisioningmodule.php) and it sill has the exact same error...theres got to be a better debug trace then this.

Edited October 8, 2020 by heapmaster

[xyzulu]

Are you using 8.0.2 ?

[heapmaster]

Yes I am, I even switched the plan to their default Plesk module and emptied the includes/hooks folder and I still get the error.

[heapmaster]

Fixed...this was caused by hidden whitespace before the starting PHP tag at the top of the file for our custom module.