If you select to store maps on the SD card the map data is still stored on the internal storage. The Android setting Apps function even shows the data usage as being on the SD card in older versions (Android 7 shows the data usage correctly).
If you check the free space before & after loading a large map with "store on SD card" selected, you will see it is in the internal storage!
If you need to store several countries (Europe) this is going to cause issues unless you have a lot of free internal storage.
I use an older Moto E (first generation) on my bike for navigation.
The Moto E has Android 4.4 KitKat and I have a SD card on the phone. I know its old, but thats why I use it.
The problem is, I select the SD card as destination for offline maps, so far so good, but the issue is that while downloading the app transfers first to the internal memory and only after finish the download it will move to SD card.
And because the internal memory of this phone is small I cannot download bigger maps, for example, I have 700MB on internal memory and Spain map is over 1GB, the app will get stuck when the internal memory is full.
Could you please fix this behavior and make the offline maps downloads (while downloading) go immediately to SD card (when SD card is selected in the app settings).