Issue: I try to get the Facility Completionist achivement. I have a list of the 13 unique facilities and I have captured all but Sky Shaker facility. I have never seen the Sky Shaker facility, and I had tried about 10 times. I know I have to wait for the fifth era in order to have the Sky Shaker facility, but by the time I have reached the fourth era all facilities have already been revealed. 

I seems like the Sky Shaker facility is programmed to appear very rarely, as opposed to the other facilities, but that doesn't make sense. Are there other (undocumented) conditions for this facility to appear? 

Specs: does not apply

Version: 1.7.5 S3

Game save: does not apply. 

Output_log.txt: does not apply

Diagnostics.html: does not apply

Registry.xml: does not apply

Finaly found it! And I got the achievement!