Bee-liever: This is a "long shot", but what version of bassenc.dll are you using? The description of this library over at un4seen reads:
"An extension that allows BASS channels to be encoded using command-line encoders with STDIN support (LAME/OGGENC/etc), or ACM codecs (on Windows) or CoreAudio codecs (on OSX/iOS), or user-provided encoders. Also features streaming of encoded data to clients directly or via Shoutcast and Icecast servers,
and PCM WAV/AIFF file writing. C/C++, Delphi, and Visual Basic APIs are included."
AFAIK, the last version of bassenc.dll supplied by MusicBee is 2.4.9.1 from way back in March 2012; being one of those "update freaks", I have been using the 2.4.14.0 version (yep same number as the latest bass.dll) from July 2018, available here:
http://www.un4seen.com/download.php?bassenc24 .
Why not try that one and see what happens??