I submitted the ticket before, and I am waiting for their slow response, the support doesn't look good even after they acquired by Circle.
Happened to me before on my NEM balanced but I think that was a viewing bug
(I don't know how it called). Transactions, History etc. all are good. My balanced turned into 0 on which way more alarming and really gaves me an extreme frustration because
"why the hell it was happened". Prior to that, as far as I can remember, I did bought that coin then after that I head to "Balance" section and checked the "Hide all 0" but no NEM on the list with balances. The bitcoin estimated value is not changed meaning the view is only the problem but overall my NEM balances there was counted.
What I did is, logout, clear everything (cookies, cache), exit browser, restart PC. Then when I came back, the balanced is now showing. Just a different case to you since your overall USD/BTC value are being deducted.