Displaying Markups (Waypoints, Routes, Lines, Shapes, Tracks) uses your device's processing power. Showing too many at once can slow down the app or cause crashes on older devices.
Tracks and Routes are especially demanding since they contain many linked Waypoints, even though they appear as a single file.
If you have a significant amount of Markups and need to improve performance, export and save your Markups as a GPX or KML file and/or delete them from your account to reduce the load on your device.
Export and save your Markups
If you don't plan on using a set of Markups anytime soon, but don't want to lose them forever, you can use the Export feature to save them to your phone or computer.
Be aware that KML and GPX files don't support onX colors and icons, so only the position and name associated with a Markup will be saved in the exported file.
Exported Markups can be restored (except for the colors and icons) using the Import feature.
Delete unnecessary Markups
To delete Markups, open the My Content menu.
Tap the Select button at the top of the menu.
Tap the check-boxes next to the Markups you want to delete, then swipe left on the bottom row of buttons and tap "Delete."
Click here for more info about managing your Markups.