TYPO3 Core

can you copy which lines are on the specific line number as I can't reproduce it here

That's the lines in the TYPO3 Core where I get the warnings:

$this->content = str_replace(
            [
                '<!--HD_' . $this->config['INTincScript_ext']['divKey'] . '-->',
                '<!--FD_' . $this->config['INTincScript_ext']['divKey'] . '-->',
            ],
            [
                implode(LF, $this->additionalHeaderData),
                implode(LF, $this->additionalFooterData),
            ],
            $this->pageRenderer->renderJavaScriptAndCssForProcessingOfUncachedContentObjects($this->content, $this->config['INTincScript_ext']['divKey'])
        );

in this function:

 public function INTincScript(ServerRequestInterface $request): void
    {
        $this->additionalHeaderData = $this->config['INTincScript_ext']['additionalHeaderData'] ?? [];
        $this->additionalFooterData = $this->config['INTincScript_ext']['additionalFooterData'] ?? [];
        if (empty($this->config['INTincScript_ext']['pageRendererState'])) {
            $this->initPageRenderer();
        } else {
            $pageRendererState = unserialize($this->config['INTincScript_ext']['pageRendererState'], ['allowed_classes' => [Locale::class]]);
            $this->pageRenderer->updateState($pageRendererState);
        }
        if (!empty($this->config['INTincScript_ext']['assetCollectorState'])) {
            $assetCollectorState = unserialize($this->config['INTincScript_ext']['assetCollectorState'], ['allowed_classes' => false]);
            GeneralUtility::makeInstance(AssetCollector::class)->updateState($assetCollectorState);
        }

        $this->recursivelyReplaceIntPlaceholdersInContent($request);
        $this->getTimeTracker()->push('Substitute header section');
        $this->INTincScript_loadJSCode();
        $this->generatePageTitle();

        $this->content = str_replace(
            [
                '<!--HD_' . $this->config['INTincScript_ext']['divKey'] . '-->',
                '<!--FD_' . $this->config['INTincScript_ext']['divKey'] . '-->',
            ],
            [
                implode(LF, $this->additionalHeaderData),
                implode(LF, $this->additionalFooterData),
            ],
            $this->pageRenderer->renderJavaScriptAndCssForProcessingOfUncachedContentObjects($this->content, $this->config['INTincScript_ext']['divKey'])
        );
        // Replace again, because header and footer data and page renderer replacements may introduce additional placeholders (see #44825)
        $this->recursivelyReplaceIntPlaceholdersInContent($request);
        $this->setAbsRefPrefix();
        $this->getTimeTracker()->pull();
    }

tested it with

page.bodyTagCObject = COA
page.bodyTagCObject {
    998 = TEXT
    998 {
        value = data-etracker-form-category="Sample" 
    }

    999 =COA_INT
    999 {

      10 = TEXT
      10.value = abc
    }
}

thanks for your feedback!