Uncaught TYPO3 Exception #1233058294: “ReflectionData_SimExchange Download” is not a valid cache entry identifier-Collection of common programming errors

I have a problem with my extbase extension in TYPO3 4.7.10. The error occurs when I place a widget via typoscript into the page. The code for this widget is the following:

plugin.tx_simexchangedownloads.widgets {
  search = USER
  search {
    userFunc = tx_extbase_core_bootstrap->run
    pluginName = Simexchangedownloadsmain
    extensionName = SimExchange Download
    controller = Download
    action = list

    settings =< plugin.tx_simexchangedownloads.settings
    persistence =< plugin.tx_simexchangedownloads.persistence
    view =< plugin.tx_simexchangedownloads.view
  }
}
lib.search < plugin.tx_simexchangedownloads.widgets.search

lib.subMenu >
lib.subMenu < lib.search

But every time I want to open the site I get the Error:

#1233058294: "ReflectionData_SimExchange Download" is not a valid cache entry identifier. (More information)

InvalidArgumentException thrown in file
/var/www/vhosts/simexchange.de/typo3/typo3_src-4.7.10/t3lib/cache/frontend/class.t3lib_cache_frontend_variablefrontend.php in line 102.

Is the problem the space in the extensionName? How can I solve it without changing the name of the extension? Is it even the right Value for extensionName? Every other value generates a different error.

The default controller for extension "SimExchangeDownload" and plugin "Simexchangedownloadsmain" can not be determined. Please check for Tx_Extbase_Utility_Extension::configurePlugin() in your ext_localconf.php.

The ext_localconf.php function says:

Tx_Extbase_Utility_Extension::configurePlugin(
    $_EXTKEY,
    'Simexchangedownloadsmain',
    array(
        'Download' => 'list, show, new, create, edit, update, delete',
        'Tag' => 'list, show, new, create, edit, update, delete',

    ),
    // non-cacheable actions
    array(
        'Download' => 'create, update, delete',
        'Tag' => 'create, update, delete',

    )
);