Invisible Pathways

Title: Invisible walkways

Summary: bug were some walkways just turn invisible for no reasons whatsoever and you cant interact at all with the ground where it was.

Steps to reproduce:
i have yet to find out how to reproduce it but it has happened in different games about 3 times now and at the moment its only with the rayaas children the darkest red colored path. i think it has something to do with the number of hearthlings because it only happens after awhile of playing

Expected Results:

Actual Results:

Notes: it seems that quitting to main menu then loading the game fixes it.

Attachments:
Before:

After:

Versions and Mods: alpha 13, 0.13.0 develop 2720 x64

System Information:

Operating System: Windows 7 Home Premium 64-bit (6.1, Build 7601) Service Pack 1 (7601.win7sp1_gdr.150928-1507)
Language: English (Regional Setting: English)
System Manufacturer: Alienware
System Model: Alienware 17
BIOS: InsydeH2O Version 03.73.02A14
Processor: Intel® Core™ i7-4700MQ CPU @ 2.40GHz (8 CPUs), ~2.4GHz
Memory: 24576MB RAM
Available OS Memory: 16384MB RAM
Page File: 9407MB used, 23359MB available
Windows Dir: C:\Windows
DirectX Version: DirectX 11
DX Setup Parameters: Not found
User DPI Setting: Using System DPI
System DPI Setting: 96 DPI (100 percent)
DWM DPI Scaling: Disabled
GPU : NVIDIA GeForce GTX 765M

In my non Rayya game, two blocks of this particular path disappeared as well. However I fixed it :
I created a new path around it, then I erased the block I didn’t want and launched the construction. My two blocks were finally here.