Hi,
I reinstalled OM from scratch on a clean phone, then tried to import a map.
First I tried tapping it in a file manager and chose OM to open the file. The progress bar stays there forever and the app hangs, I had to kill it.
Then I tried with the internal import function and got the same result.
The file was around 2GB. A 300MB one worked but took quite a bit of time, compared to the time it takes to copy the same file with SolidExplorer.