bref: FastCgiCommunicationFailed on every second request

Description:

I am seeing a 502 gateway error on every second request made to my api. In cloudwatch logs I can see the following:

START RequestId: 3711f7ba-56d6-41d6-9e70-decaa7f0fcdf Version: $LATEST
--
Error communicating with PHP-FPM to read the HTTP response. A root cause of this can be that the Lambda (or PHP) timed out, for example when trying to connect to a remote API or database, if this happens continuously check for those! Bref will restart PHP-FPM now. Original exception message: hollodotme\FastCGI\Exceptions\WriteFailedException Failed to write request to socket [broken pipe]
[18-Jan-2021 16:54:24] NOTICE: Terminating ...
[18-Jan-2021 16:54:24] NOTICE: exiting, bye-bye!
2021-01-18 16:54:24.566 +0000 (14 14) info: attempt daemon connection via 'newrelic-daemon.REDACTED:31339'
2021-01-18 16:54:24.568 +0000 (14 14) info: Daemon connection settings specify a host different from the local host. Daemon will not be started by the Agent.
2021-01-18 16:54:24.568 +0000 (14 14) info: New Relic 9.15.0.293 ("vanilla" - "bab8316e39f6") [daemon='newrelic-daemon.int.bdry.com:31339'  php='7.4.14' zts=no sapi='fpm-fcgi'  pid=14 ppid=7 uid=993 euid=993 gid=990 egid=990 backtrace=yes startup=init os='Linux' rel='4.14.203-112.332.amzn2.x86_64' mach='x86_64' ver='#1 SMP Wed Nov 4 20' node='169.254.153.173']
[18-Jan-2021 16:54:24] NOTICE: fpm is running, pid 14
[18-Jan-2021 16:54:24] NOTICE: ready to handle connections
3711f7ba-56d6-41d6-9e70-decaa7f0fcdf	Invoke Error	{     "errorType": "Bref\\Event\\Http\\FastCgi\\FastCgiCommunicationFailed",     "errorMessage": "",     "stack": [         "#0 /var/task/vendor/bref/bref/src/Event/Http/HttpHandler.php(25): Bref\\Event\\Http\\FpmHandler->handleRequest()",         "#1 /var/task/vendor/bref/bref/src/Runtime/Invoker.php(29): Bref\\Event\\Http\\HttpHandler->handle()",         "#2 /var/task/vendor/bref/bref/src/Runtime/LambdaRuntime.php(102): Bref\\Runtime\\Invoker->invoke()",         "#3 /opt/bootstrap(43): Bref\\Runtime\\LambdaRuntime->processNextEvent()",         "#4 {main}"     ] }
END RequestId: 3711f7ba-56d6-41d6-9e70-decaa7f0fcdf
REPORT RequestId: 3711f7ba-56d6-41d6-9e70-decaa7f0fcdf	Duration: 37.85 ms	Billed Duration: 38 ms	Memory Size: 1024 MB	Max Memory Used: 83 MB

Currently the endpoint simply returns a 200. There are no database connections. The only connection I can think of is to an internal fargate service running the new relic daemon (this support was just added recently to bref extensions).

How to reproduce:

Bref: 1.1.3 Extensions: bref:extra.newrelic-php-74 - 0.9.5 Application Framework: Slim 4 Runtime: provided.al2

I am also using a VPC with my Lambda function. It has 2 public and and private subnets with the expected NAT gateway.