When enabling debug via the apostrophe key in a PIE session, print string is disabled and when you close debug print string works again.
However if you press Escape to close the PIE session with the debug information on screen then it does not re-enable print string until you reselect Development build configuration and restart the editor.
Steps to reproduce in a new project: (works 9/10 times)
Add Print String to Tick on the character Blueprint
While PIE is active press Apostrophe to enter debug mode
Press Escape to exit PIE session
No more Print String until editor restart
I have seen other forum posts regarding this topic but no working solution was offered or steps to reproduce. (I have included links for convenience)
EDIT: I forgot to mention it does still print to the log but not to the screen.
Thanks for trying that. It also reproduces in the official 4.15 release and out internal builds. I’ve logged it as JIRA UE-41988 and our developers will be investigating further. Follow that link to monitor the status of the bug report.
The bug is still behaving as described, however, if you follow the steps provided to have debug messages stop displaying on screen, then reactivating debug mode and turning on debug messaging with ctrl-tab and exiting PIE they will work as normal.
It would seem to be the case that exiting of a PIE session with the debugger on just doesn’t reset the messaging variable.