horizon: RuntimeException - Unable to write output.

• Horizon Version: 3.6.0
• Laravel Version: 6.14.0
• PHP Version: 7.4.2
• Redis Driver & Version: predis/phpredis 5.1.1
• Database Driver & Version: MySQL 8.0.17

Description:

We did an simultaneous upgrade from CentOS 7 to 8 and from PHP 7.3 to 7.4 and we started to get Symfony\Component\Console\Exception\RuntimeException - Unable to write output exceptions from the Horizon Supervisor. Sometimes restarting Horizon or rebooting the machine fixes the issue for a while. I have no idea what might be causing this.

Stacktrace:

Symfony\Component\Console\Exception\RuntimeException Unable to write output. 
    /var/www/projectname/releases/7/vendor/symfony/console/Output/StreamOutput.php:79 Symfony\Component\Console\Output\StreamOutput::doWrite
    /var/www/projectname/releases/7/vendor/symfony/console/Output/Output.php:166 Symfony\Component\Console\Output\Output::write
    /var/www/projectname/releases/7/vendor/symfony/console/Style/OutputStyle.php:56 Symfony\Component\Console\Style\OutputStyle::write
    /var/www/projectname/releases/7/vendor/symfony/console/Style/SymfonyStyle.php:395 Symfony\Component\Console\Style\SymfonyStyle::write
    /var/www/projectname/releases/7/vendor/laravel/horizon/src/Console/SupervisorCommand.php:83 Laravel\Horizon\Console\SupervisorCommand::Laravel\Horizon\Console\{closure}
    [internal] call_user_func
    /var/www/projectname/releases/7/vendor/laravel/horizon/src/Supervisor.php:471 Laravel\Horizon\Supervisor::output
    /var/www/projectname/releases/7/vendor/laravel/horizon/src/Supervisor.php:134 Laravel\Horizon\Supervisor::Laravel\Horizon\{closure}
    [internal] call_user_func
    /var/www/projectname/releases/7/vendor/laravel/horizon/src/ProcessPool.php:165 Laravel\Horizon\ProcessPool::Laravel\Horizon\{closure}
    /var/www/projectname/releases/7/vendor/symfony/process/Process.php:1328 Symfony\Component\Process\Process::Symfony\Component\Process\{closure}
    /var/www/projectname/releases/7/vendor/symfony/process/Process.php:1441 Symfony\Component\Process\Process::readPipes
    /var/www/projectname/releases/7/vendor/symfony/process/Process.php:1359 Symfony\Component\Process\Process::updateStatus
    /var/www/projectname/releases/7/vendor/symfony/process/Process.php:854 Symfony\Component\Process\Process::isRunning
    /var/www/projectname/releases/7/vendor/laravel/horizon/src/ProcessPool.php:297 Laravel\Horizon\ProcessPool::Laravel\Horizon\{closure}
    [internal] array_filter
    /var/www/projectname/releases/7/vendor/laravel/framework/src/Illuminate/Support/Arr.php:611 Illuminate\Support\Arr::where
    /var/www/projectname/releases/7/vendor/laravel/framework/src/Illuminate/Support/Collection.php:352 Illuminate\Support\Collection::filter
    /var/www/projectname/releases/7/vendor/laravel/horizon/src/ProcessPool.php:298 Laravel\Horizon\ProcessPool::runningProcesses
    /var/www/projectname/releases/7/vendor/laravel/framework/src/Illuminate/Support/HigherOrderCollectionProxy.php:60 Illuminate\Support\HigherOrderCollectionProxy::Illuminate\Support\{closure}
    [internal] array_map
    /var/www/projectname/releases/7/vendor/laravel/framework/src/Illuminate/Support/Collection.php:638 Illuminate\Support\Collection::map
    /var/www/projectname/releases/7/vendor/laravel/framework/src/Illuminate/Support/HigherOrderCollectionProxy.php:61 Illuminate\Support\HigherOrderCollectionProxy::__call
    /var/www/projectname/releases/7/vendor/laravel/horizon/src/Supervisor.php:232 Laravel\Horizon\Supervisor::terminate
    /var/www/projectname/releases/7/vendor/laravel/horizon/src/ListensForSignals.php:52 Laravel\Horizon\Supervisor::processPendingSignals
    /var/www/projectname/releases/7/vendor/laravel/horizon/src/Supervisor.php:292 Laravel\Horizon\Supervisor::loop
    /var/www/projectname/releases/7/vendor/laravel/horizon/src/Supervisor.php:267 Laravel\Horizon\Supervisor::monitor
    /var/www/projectname/releases/7/vendor/laravel/horizon/src/Console/SupervisorCommand.php:92 Laravel\Horizon\Console\SupervisorCommand::start
    /var/www/projectname/releases/7/vendor/laravel/horizon/src/Console/SupervisorCommand.php:67 Laravel\Horizon\Console\SupervisorCommand::handle
    [internal] call_user_func_array
    /var/www/projectname/releases/7/vendor/laravel/framework/src/Illuminate/Container/BoundMethod.php:32 Illuminate\Container\BoundMethod::Illuminate\Container\{closure}
    /var/www/projectname/releases/7/vendor/laravel/framework/src/Illuminate/Container/Util.php:36 Illuminate\Container\Util::unwrapIfClosure
    /var/www/projectname/releases/7/vendor/laravel/framework/src/Illuminate/Container/BoundMethod.php:90 Illuminate\Container\BoundMethod::callBoundMethod
    /var/www/projectname/releases/7/vendor/laravel/framework/src/Illuminate/Container/BoundMethod.php:34 Illuminate\Container\BoundMethod::call
    /var/www/projectname/releases/7/vendor/laravel/framework/src/Illuminate/Container/Container.php:590 Illuminate\Container\Container::call
    /var/www/projectname/releases/7/vendor/laravel/framework/src/Illuminate/Console/Command.php:173 Illuminate\Console\Command::execute
    /var/www/projectname/releases/7/vendor/symfony/console/Command/Command.php:255 Symfony\Component\Console\Command\Command::run
    /var/www/projectname/releases/7/vendor/laravel/framework/src/Illuminate/Console/Command.php:160 Illuminate\Console\Command::run
    /var/www/projectname/releases/7/vendor/symfony/console/Application.php:1012 Symfony\Component\Console\Application::doRunCommand
    /var/www/projectname/releases/7/vendor/symfony/console/Application.php:272 Symfony\Component\Console\Application::doRun
    /var/www/projectname/releases/7/vendor/symfony/console/Application.php:148 Symfony\Component\Console\Application::run
    /var/www/projectname/releases/7/vendor/laravel/framework/src/Illuminate/Console/Application.php:93 Illuminate\Console\Application::run
    /var/www/projectname/releases/7/vendor/laravel/framework/src/Illuminate/Foundation/Console/Kernel.php:131 Illuminate\Foundation\Console\Kernel::handle
    /var/www/projectname/releases/7/artisan:35 [main]