If just one or two, remove the app, do a System Restart, and reinstall the offending app. If it is doing it with "every" app, then maybe just start simple and progress upwards.
1. From within Roku, do a System Restart. (Settings...System...System Restart)
2. Make sure your Roku is up to date. (Settings...System...System Update...Check Now)
2. Unplug your Roku for a while. (Have seen increasing # of posts indicating this solves a lot of unexplained problems.)
3. Do a Factory Reset of your device. (Settings..System..Advanced System Settings..Factory Reset)
See if any of the above helps you out and post back whatever steps you have taken if still having problems or if a particular step worked for you.
Also include your Roku model Number. More detail the better when troubleshooting.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660x, Premiere+ 3921, Express 4k+ 3941