I have had two errors so far that were similar. Both times, I looked up an item through Shop Search and was purchasing from an NPC shop. The first time, I got an error similar to the one I copied below, received a 15% off buff, and was not given the item. I repeated the process and was able to buy the item the second time with no issues. Then a couple of item purchases later, I purchased an item again from an NPC store and got this error:

"Fatal error: Uncaught exception 'GuzzleHttpExceptionClientException' with message 'Client error: 404' in /www/subeta.net/vendor/guzzlehttp/guzzle/src/Middleware.php:69 Stack trace: /www/subeta.net/vendor/guzzlehttp/promises/src/Promise.php(199): GuzzleHttpMiddleware::GuzzleHttp{closure}(Object(GuzzleHttpPsr7Response)) /www/subeta.net/vendor/guzzlehttp/promises/src/Promise.php(152): GuzzleHttpPromisePromise::callHandler(1, Object(GuzzleHttpPsr7Response), Array) /www/subeta.net/vendor/guzzlehttp/promises/src/TaskQueue.php(60): GuzzleHttpPromisePromise::GuzzleHttpPromise{closure}() /www/subeta.net/vendor/guzzlehttp/guzzle/src/Handler/CurlMultiHandler.php(96): GuzzleHttpPromiseTaskQueue->run() /www/subeta.net/vendor/guzzlehttp/guzzle/src/Handler/CurlMultiHandler.php(123): GuzzleHttpHandlerCurlMultiHandler->tick() /www/subeta.net/vendor/guzzlehttp/promises/src/Promise.php(240): GuzzleHttpHandlerCurlMultiHandler->execute(true) /www/subeta.net/vendor/guzzlehttp/promises/src/Promise.php(21 in /www/subeta.net/vendor/guzzlehttp/guzzle/src/Middleware.php on line 69"

This time, it gave me the item, despite the error.

edit: I just had the same exact problem when buying from a user shop.

I believe is having the same issue.

I get:

Fatal error: Uncaught exception 'GuzzleHttpExceptionClientException' with message 'Client error: 404' in /www/subeta.net/vendor/guzzlehttp/guzzle/src/Middleware.php:69 Stack trace: /www/subeta.net/vendor/guzzlehttp/promises/src/Promise.php(199): GuzzleHttpMiddleware::GuzzleHttp{closure}(Object(GuzzleHttpPsr7Response)) /www/subeta.net/vendor/guzzlehttp/promises/src/Promise.php(152): GuzzleHttpPromisePromise::callHandler(1, Object(GuzzleHttpPsr7Response), Array) /www/subeta.net/vendor/guzzlehttp/promises/src/TaskQueue.php(60): GuzzleHttpPromisePromise::GuzzleHttpPromise{closure}() /www/subeta.net/vendor/guzzlehttp/guzzle/src/Handler/CurlMultiHandler.php(96): GuzzleHttpPromiseTaskQueue->run() /www/subeta.net/vendor/guzzlehttp/guzzle/src/Handler/CurlMultiHandler.php(123): GuzzleHttpHandlerCurlMultiHandler->tick() /www/subeta.net/vendor/guzzlehttp/promises/src/Promise.php(240): GuzzleHttpHandlerCurlMultiHandler->execute(true) /www/subeta.net/vendor/guzzlehttp/promises/src/Promise.php(21 in /www/subeta.net/vendor/guzzlehttp/guzzle/src/Middleware.php on line 69

Though I am receiving mine trying to complete a quest. I have the items in my inventory, click finish, receive an error message, and the items disappear from my inventory. Even submitting a ticket has resulted in the long error message from hell.