Ran into an issue after the Summer 19 preview in my sandbox. I have a Visualforce page re-directing to a lightning URL Accessible component passing in a parameter, here is the controller code:
PageReference pr = new PageReference('/lightning/cmp/c__SomeComponent?someParam='+this.someParam);
Everything is working fine in production; however, in the Sandbox the PageReference state no longer registers the parameter when the lightning page initializes.
When I do a debug, I see that the parameter is being passed from my VF controller as a part of the URL; however, when the page loads the parameter is no longer listed in the URL. Additionally, I checked what was actually being processed in the state:
It did not contain the attribute I was passing.
Color me confused.