I doubt it can be classified as a bug unless the issue can be reproduced.
Can you do that?
Are Photoshop and OS fully updated and have you performed the usual trouble-shooting routines (trashing prefs by keeping command-alt-shift/ctrl-alt-shift pressed while starting Photoshop, 3rd party plug-ins deactivation, system maintenance, font validation, etc.)?
Does turning off OpenGL in the Performance Preferences and restarting Photoshop have any bearing on the issue?