It's old issue (6 April), and i think is reported only to Poloniex, infact in this tweet
https://mobile.twitter.com/golemproject/status/892321003405283328 on the recent maintenance (last days of July and early August) of gnt wallet in the above exchange, golemproject says
We're not contacting them, especially after their violent reaction when we pointed out a flaw in their system earlier this year.
Anyway the gnt wallet maintenance on Poloniex has lasted at least one week, and it is presumed that the reason was the one you mentioned