Am noticing something similar but not sure if its the same exactly
And I think its taken me about 2 weeks to actually catch it in the act.
AM using an MKR1000 and I thought it was the board that was pooched but I changed my debug output method and noticed it has sent some data on two occasions but that TS was reporting last connected (x) amount of time which was behind the sent data connection by an hour or so.
Also seeing a very sluggish site too often not refreshing properly and wonder if that is linked somehow ?