The issue is likely just world partition/composition.
When you import tiles, if your world minimap is open, the engine will attempt to render the tiles and print out the minimap.
This causes the engine to crash out with either Vram or Ram (usually vram).
To avoid it, in 4.24 at least, it was possible to close everything out and import things.
Or, and this will always work, to batch process the tiles in sets of 9 or so - which should compute in a manner of a few minute tops.
All map tiles/heitmaps should always be below 8k in file size. Even if it is possible to edit the engine source to allow larger files.
As far as world partition (whatever the one from the latest engine versions is involved) i have yet to see a single forum post claiming that the system works at all. I doubt you’d have much luck in “converting” things to it…