TYPO3 Core

I noticed this problem in a special situation in my extbase plugin.
I have a classic structure with show,submit,success actions.
show displays a normal form
submit do some checks and when the check is false I forward back to show .

In my show ation I use $this->configurationManager->getContentObject(); to read out some informations out of the content element.
After the I made some checks in the submit action I forward back to show , in this situation the data of $this->configurationManager->getContentObject(); is empty.

The reason for this is I noticed happens because I make a mail submit in the submit action and use FluidEmail
$mail = GeneralUtility::makeInstance(\TYPO3\CMS\Core\Mail\FluidEmail::class);

When this line is added the getContentObject() returns an empty ContentObjectRenderer .

My workaround for this problem was

$contentObject = $this->configurationManager->getContentObject();
// do something with email like  GeneralUtility::makeInstance(\TYPO3\CMS\Core\Mail\FluidEmail::class);
$this->configurationManager->setContentObject($contentObject);

Daniel Siepmann noticed that inside the constructor of the StandaloneView the contentObjects gets 'resetted'
https://github.com/TYPO3/TYPO3.CMS/blob/2f6fb781a2f9387c875cb176c2842426f70d52c8/typo3/sysext/fluid/Classes/View/StandaloneView.php#L45