I downloaded maps to system storage then remembered to change storage to SD card. I now find that I still have 4GB used in /storage/emulated/0/Android/data/com.myrouteapp.navigation/here-cache
So changing the storage location does not remove stored maps and changing back to the original storage location does not re register the existing maps even though they are still there.
My next move is to reinstall Navigation for a clean start.
In the Android Application Manager "Navigation" is listed as using 4.12 GB of data on the SD card even though the SD card only has 1.5 GB data on it in total!
On using the application manager delete all data for this app option the data was deleted even though it was listed at the wrong location.
On reloading a map it went in internal storage, next a full reinstall.
This is on a Samsung SM-T520
Reinstalled Navigation on the Samsung tablet - no change everything goes in internal storage even though and the app itself and the 'Application Manager' say its in the SD card.
Now checked my phone, also set to download maps to the SD card still downloads to internal memory.
In this case the 'Application Manager' correctly reports the memory usage as internal.
The phone is a Blackview BV8000Pro running Android 7.0