I have multiple .tiff + .tfw files in EPSG:3067, which I need to reproject to EPSG:3878. I tried to do it with FME, and succeeded, kind of. The geotiffs are placed well, but some weird white area appears between the grid (see image attached) when I add the orthophotos to ArcMap 10.4. I used CsmapReprojector, "ignore heights" was selected and interpolation type was Bicubic and Cell Size was "Preserve Cells". I also defined source and destination coordinates manually to 3067 and 3878.
So what did I do wrong while 3878 reprojection looks like this:
While it should look like this: