TYPO3 - how to remove cHash in f:link.action to uncached action?

Question

EDIT: the answer of @Wolffc is totally correct - i had a false return value so the problem was between chair and screen.

TYPO3 10.4.8

I’m generating a link in a Mail with <f:link.action> to validate a subscription to a Course.

It must not be cached, so i can check if the link is already clicked, but there is a cHash added to the link.

<f:link.action
    action="validate"
    pluginName="Coursevalidation"
    extensionName="myextension"
    controller="Course"
    pageUid="1"
    absolute="1"
    pageType="1921"
    noCache="1"
    noCacheHash="1"
    arguments="{validationHash: subscription.validationHash, course:course, subscription:subscription}"
>Link</f:link.action>

the documentation says noCache and noCacheHash should not be used (“you should not need this”), and it makes no difference if I add it.

The PageType is uncached, 1921.config.no_cache = 1

The generated link results in (linebreaks for better readability):

https://mydomain.ddev.site/email-validation
?no_cache=1
&tx_myextension_coursevalidation%5Baction%5D=validate
&tx_myextension_coursevalidation%5Bcontroller%5D=Course
&tx_myextension_coursevalidation%5Bcourse%5D=3
&tx_myextension_coursevalidation%5Bsubscription%5D=30
&tx_myextension_coursevalidation%5BvalidationHash%5D=40e83[...thats long ;)...]0d65c
&cHash=5d7688ac4f04a2d31a98f2cffb792e51

As you can see, theres a cHash. First klick on the Link triggers my mechanism to check everything and set the subscription to valid , and redirect to the “Success”-Page, what is exactly what it should do.

The second klick opens the success-page too, but there should be the message “Already validated”. That page is opened, when I call the Link without the cHash.

Why is there a cHash added and how can I remove it?

Thanks :)