after Summer 18 release on our Sandbox, we encountered couple issues, biggest being:

If i send custom class (with couple maps containing dates as keys) to aura, then stringify it and send it back as raw String to apex, then convert it to said class, I get "FATAL_ERROR System.JSONException: Invalid format: "Tue May 01 00:00:00 GMT 2018" at [line:1, column:10928]".
Prior to Summer 18, this was not the case, so i'm pretty sure it's because of the new Release.

Any ideas on what to do with it? I'm not changing the date values in any way in Aura, just resending my custom class from aura to apex.