Are you able to reproduce this issue in a blank template project like First or Third Person Template? If you can get this issue to reproduce in a blank project, or if you are able to send the .exe with the issue occurring that could help me report the issue or help you find a fix.
I just attempted to reproduce this issue in a new third person blueprint project, but was unable to get the same critical error to appear.
I got the log “LogGameMode: FindPlayerStart: PATHS NOT DEFINED or NO PLAYERSTART with positive rating” followed by a fatal error. But, it turns out that the fatal error is unrelated and that my above “error” message is harmless.