1. Which version of PhantomJS are you using? Tip: run phantomjs --version.
   2.1.1
2. What steps will reproduce the problem?
   Start phantomjs and leave it running
3. Which operating system are you using?
   OSX 10.11.4
4. Did you use binary PhantomJS or did you compile it from source?
   Binary from npm phantomjs-prebuilt@2.1.7
5. Please provide any additional information below.

These guys had the same issue: owncloud/client#4294

Console "Diagnostic and Usage Messages" log is filled with the following

19.05.16 09:35:10,050 airportd[66]: com.apple.message.domain: com.apple.wifi.internal.scanning
com.apple.message.error: No Error
com.apple.message.duration: 3
com.apple.message.process_name: phantomjs
com.apple.message.mac_address: ac:bc:32:b2:ff:69
SenderMachUUID: D1FCF015-F884-34A4-87C2-5D94E1EBC21D

In System log

19.05.16 09:36:34,126 airportd[66]: SecTaskLoadEntitlements failed error=22

Ping to wifi router usually is 1-3ms but at these moments it drops to around 100ms. It affects network speed and calls in Google hangouts etc are performing really bad.