However it soon became clear that the cause was a bug with the 'FM' switches in OpenTx. Fortunately there's a workaround which I've incorporated in F3J version 3.0.1. The workaround is compatible with all supported transmitters. More details below.
Problem descriptionIn version 3.0.0 of the F3J setup, a track is played when Speed mode (FM7) is engaged. This works fine on the X9D and Horus, however on the X9E it's not possible to specify FM7 - if you try to select it via the user interface, it immediately changes to '!FM7'. An issue has been raised on Github.
|SF9 triggered by FM7, but due to a bug it cannot be used with X9E|
The workaroundThe workaround involves creating a logical switch (L13) to emulate FM7. It returns TRUE if FM0 - FM6 are all FALSE. In other words, if all flight modes 1 to 6 are not active, then flight mode 7 must be active. (Flight mode 8 is ignored since it's not used in this setup.) When used in a special function, L13 triggers an action on a FALSE to TRUE transition, just like the other FMx switches.
|L13 emulates buggy FM7. Delay of 0.1 sec suppresses True at startup.|
|SF9 with FM7 replaced by L13|
The workaround is incorporated in F3J version 3.0.1.