Desert next to Mesa biome separated by unnatural straight line for hundreds of blocks

[jcobol]

Describe the bug
I encountered a Desert next to a Mesa biome separated by unnatural straight line for hundreds of blocks. Flew for awhile to observe and didn't reach the end of it. The terrain itself looks fine, though.

To Reproduce
Describe the steps it takes to reproduce the bug
Example:

1. Join the game
2. Execute command /tpll 40.000 40.000
3. Observe the desert sand vs. hardened clay separated by a straight line for "miles".

Expected behavior
There is no such line on Google maps satellite view.

Screenshots
If applicable, add screenshots to help explain your problem.

Error Logs
If applicable, paste your server logs into https://mclo.gs/ and include the link here.

Version (please complete the following information):

• What version of TerraPlusPlus are you using? terraplusplus-1.1.0.578-1.12.2.jar
• What version of the BTE Modpack or Server pack are you running? (If applicable)