Reported from a real shack: JTDX decoding FT4 came through as Q65. A
Decode carries a one-character marker rather than a mode name, and the
forks do not agree on that one — so the character alone cannot answer,
and its wrong answer reached everything behind it: new mode, new slot,
the mode filter, all computed against a mode nobody was using.
The sending program's own Status settles it. It comes from that program,
names the mode in full, and is re-sent whenever it changes, so it knows
what is being decoded in a way one character never can. Only the
ambiguous marker consults it: the ones both forks agree on keep
answering from the table, Status or no Status, and with no Status at all
':' still reads as Q65 — WSJT-X's meaning, the older and commoner.