It's barely visible, but it seems that generating tiles like this can bug out the new (and very good looking) transition between out-of-map and a normal tile. This happened in 0.17.3 in Diggy. It doesn't always happen, so it seems to be related to insert order of non-out-of-map tiles.
[0.17.3] Minor tile display bug with dirt next to out-of-map
Re: [0.17.3] Minor tile display bug with dirt next to out-of-map
Thanks for the report however I can't reproduce this. Can you post a save file that shows the problem and your log file?
If you want to get ahold of me I'm almost always on Discord.