[NTG-context] LMTX fails with custom tags (MkIV continues to work)

Documents fail with an error when they include \startelement[tagname]. This started on or before the 2020.11.17T12:42 LMTX update, and continues with 2020.11.18 19:16 LMTX. MkIV continues to work as expected. Example: \setelementbackendtag[myTag] \setelementnature[myTag][mixed] \starttext  \startelement[myTag]                     % <---   This works with MkIV but fails with LMTX, complaining: {\tt   tex error on line 17 in file G:/extract.mkvi: The file ended   when scanning an argument.}   It works in LMTX when marked lines are removed, but\unknown  \stopelement                              % <--- \stoptext -- Rik