I got into the same problem with APM 2.8 , whenever i want to write the WP an enexpected error message appear. i tried to change the version of mission planner from 1.3.70 to 1.3.72 but it didn’t work , actually it did work before that on the first version 1.3.70 but i don’t know why it doesn’t now .
since i am participating on a competition can someone please help me on this point as soon as possible .