Here is a workaround https://stackoverflow.com/a/68318584/1122517

Same problem here. It occurs intermittently.

This is my solution. In my program, below code called in many times and seems this evaluateJavascript waits until its completionHandler arrive with blocking other process. In other words this produces lots of messages which can be processed than expected. Finally it blocks process. webView?.evaluateJavaScript(functionWithParams, completionHandler: { (result, error) in }) So my solution is to run Run loop while it waits its completionHandler. }

If happens, just bump up your version. That works to me.