SUMMARY *** NOTE: If you are reporting a crash, please try to attach a backtrace with debug symbols. See https://community.kde.org/Guidelines_and_HOWTOs/Debugging/How_to_create_useful_crash_reports *** STEPS TO REPRODUCE 1. Use the software for an hour or more to draw 2. 3. OBSERVED RESULT All tools and brushes stop working EXPECTED RESULT SOFTWARE/OS VERSIONS Windows: macOS: Linux/KDE Plasma: (available in About System) KDE Plasma Version: KDE Frameworks Version: Qt Version: ADDITIONAL INFORMATION
Um, sorry, but this simply isn't enough information to do anything. If restarting the PC makes a difference it sounds like it's an issue specific to your system. It would be better to ask your support question on krita-artists.org, where there might be people who have had the same experience. But as it is, we cannot help you with this report.