Synthesis Inexplicably "Interrupted" + Lost Materials

Platform: Windows
ISP: Metrocast
Type of Internet Connection: cable modem
Internet Connection Speed: 40Mbps
Date & Time: March 22, 2017 approx. 9:40pm EDT
Frequency: 2 times
Character Name: Nakti
Race: Hume
World: Asura
Main Job: Dragoon
Support Job: Samurai
Area and Coordinates: Carpenter's Guild lower level, North Sandoria
Party or Solo: Solo
NPC Name: not applicable
Monster Name: not applicable
Steps:
1. Wind Crystal + 2 mahogany lumber
2. synthesize

I did 10 or 11 of these synths. I paid for Advanced Synthesis Support which brought me to the skill cap of Mahogany Poles (the synth I was doing).

Two (2) of the synths inexplicably resulted in an "interrupted" message which automatically resulted in lost materials.

I was the only player in the lower Carpenter's Guild and my chat log showed only one other person synthesizing nearby (upstairs Carpenter's Guild maybe). There was no visible lag, there was no one casting spells on me, and I certainly wasn't zoning from North Sandoria to somewhere else.

One other thing of note, a couple of the synths completed (successfully) far more quickly than usual.

I did additional synthing (but not Mahogany Poles) in my Mog Garden soon afterward and did not experience the "interrupted" error.