Hi, we are experiencing a strange issue with our Web App. Our web app runs entirely on the same domain , and we are making several AJAX requests to the same server. The Error occurs only on Iphones, the app works completely fine on androids and computers.
Most of the requests work fine, but suddenly, one specific request always fails with the following error:
XMLHttpRequest cannot load https://demo2.artios.cz/app37g/v105/php/endpoint.php due to access control checks
What we have checked so far:
✅ CORS headers seem correct. Also we operate entirely on the same domain, client and server.
✅ The same request works fine in computer and android devices.
✅ The issue occurs only on iPhone (tested on Chrome and Safari).
✅ Some requests to the same endpoint pass, but suddenly, this specific request always fails.
✅ There is no OPTIONS preflight request logged in the network tab, but we use only simple requests.
✅ We are making a POST request with multipart/form-data.
What is Your advice, or where I can find more info about this error? We do not think the CORS is the problem. We have tried to inspect with WebInspector but with no relevant answers. Thank You very much!