Map update fails with storage error

I have only 16Gb of internal storage on my Samsung A320 so all Locus folders are located on my SD card. But I have freed up as much internal storage as I can so have 2Gb free which is usually adequate.

I have tried to update downloaded LoMaps of North and South France, which are about 2.5 Gb each. But it fails and I get a warning from system saying internal storage is full. I assume this is because the map is downloaded to main storage and then transferred to SD card.

When I first downloaded these maps in 2022 I didn't have a problem although it is almost certain I had less free storage.

I'm wondering whether it tries to use main storage when it is an update, but goes straight to SD card if it is a new download? I don't want to remove the existing download in case I then can't download a new one.

Using v 4.17.1

How can I update the maps?