Or maybe the web server is decoding it before it makes it to thredds...
It would seem that thredds is converting the %3D to "=" in its head, then failing on the string comparison. Just my guess though.
NOTE: All email exchanges with Unidata User Support are recorded in the Unidata inquiry tracking system and then made publicly available through the web. If you do not want to have your interactions made available in this way, you must let us know in each email you send to us.