Cache build up might cause app to freeze and crash
App may need an update
App may not be compatible with your device
Troubleshooting:
Reboot your device by holding power key and select power off and press okay to confirm.
Check whether your Sonim phone software is up to date. Go to settings >About phone > System updates.
Updating an App can help solve this issue, Got o Google play store and select My apps and select app that isn’t working properly and check if there is any update available. App update can provide security improvements and enhancements that may fix this issue.
You can try to force stop that application which will completely shut app down, including any background services that may cause your issue. Go to settings > Apps >Select the app and touch Force stop.