Custom pages not working when ext is enabled

[ernestpasnik]

I mean custom pages like that https://www.phpbb.com/support/docs/en/3.1/kb/article/add-a-new-custom-page-to-phpbb
An error appear:

Fatal error: Uncaught Twig\Error\LoaderError: Looks like you try to load a template outside configured directories (../assets/css/font-awesome.min.css) in "@stevotvr_flair/event/overall_header_head_append.html" at line 2. in /var/www/httpdocs/vendor/twig/twig/src/Loader/FilesystemLoader.php:291 Stack trace: #0 /var/www/httpdocs/vendor/twig/twig/src/Loader/FilesystemLoader.php(209): Twig\Loader\FilesystemLoader->validateName('../assets/css/f...') #1 /var/www/httpdocs/phpbb/template/twig/loader.php(135): Twig\Loader\FilesystemLoader->findTemplate('../assets/css/f...', true) #2 /var/www/httpdocs/vendor/twig/twig/src/Loader/FilesystemLoader.php(150): phpbb\template\twig\loader->findTemplate('../assets/css/f...') #3 /var/www/httpdocs/phpbb/template/twig/environment.php(313): Twig\Loader\FilesystemLoader->getCacheKey('../assets/css/f...') #4 /var/www/httpdocs/cache/production/twig/dc/dcee1e4533478e33168dc8f59affbdf0f87ef47628eb93479584be390e68c58a.php(45): phpbb\template\twig\environment->findTemplate('../assets/css/f...') #5 /var/www/httpdocs/vendor/twig/twig/src/Template.php(405): __TwigTemplate_92fd48a68f66f938e4eb17880ff9bef1d1e33fa45fbf589cc0ff75a9a170bc2a->doDisplay(Array, Array) #6 /var/www/httpdocs/vendor/twig/twig/src/Template.php(378): Twig\Template->displayWithErrorHandling(Array, Array) #7 /var/www/httpdocs/cache/production/twig/4c/4cbd42adc092dc378dfde29e85ccd26f5f520a8a983084f07e32e07fe6a19df7.php(350): Twig\Template->display(Array) #8 /var/www/httpdocs/vendor/twig/twig/src/Template.php(405): __TwigTemplate_616f6a9089f628ad986ef5597e638f53b20a856c344759b522bfc46bb23d59b7->doDisplay(Array, Array) #9 /var/www/httpdocs/vendor/twig/twig/src/Template.php(378): Twig\Template->displayWithErrorHandling(Array, Array) #10 /var/www/httpdocs/cache/production/twig/a2/a21faa059f9825fcb9b1528523057e07f2397757b6af3ba92c4738df39a1c461.php(44): Twig\Template->display(Array) #11 /var/www/httpdocs/vendor/twig/twig/src/Template.php(405): __TwigTemplate_fe66ef5979b07a6ac1226c16ee123d924305c6921afda099d29592ecd876a5b4->doDisplay(Array, Array) #12 /var/www/httpdocs/vendor/twig/twig/src/Template.php(378): Twig\Template->displayWithErrorHandling(Array, Array) #13 /var/www/httpdocs/vendor/twig/twig/src/Template.php(390): Twig\Template->display(Array) #14 /var/www/httpdocs/vendor/twig/twig/src/TemplateWrapper.php(45): Twig\Template->render(Array, Array) #15 /var/www/httpdocs/vendor/twig/twig/src/Environment.php(318): Twig\TemplateWrapper->render(Array) #16 /var/www/httpdocs/phpbb/template/twig/environment.php(224): Twig\Environment->render('www/servermanag...', Array) #17 /var/www/httpdocs/phpbb/template/twig/environment.php(194): phpbb\template\twig\environment->display_with_assets('www/servermanag...', Array) #18 /var/www/httpdocs/phpbb/template/twig/twig.php(317): phpbb\template\twig\environment->display('www/servermanag...', Array) #19 /var/www/httpdocs/includes/functions.php(4273): phpbb\template\twig\twig->display('body') #20 /var/www/httpdocs/www/servermanagement.php(198): page_footer() #21 {main} thrown in /var/www/httpdocs/vendor/twig/twig/src/Loader/FilesystemLoader.php on line 291