Few years ago, ehen my Roku express box started not being able to play installed app channels, after what appeared to be a firmware update, e.g. BzbC iPlayer app, apps half-started and either exited or crashed or loaded slow and were slow or partially functioning:
I hard power reset the box nothing fixed. Then reset back to factory settings from system menu and restarted. Login setup with same Roku userid then it re-insalled all the apps I had installed before, took a while, and back to a functioning unit and all the apps worked again
Try similar if updates or corruption on box.
