Changing time signature with two differents clefs in linked staves causes false "transposition"

Nightly November 5 (0ff91aa) / Windows 7

1. Open "My First Score"

2. "I" -> select staff1 -> Add linked staff (bass clef) ->Ok

3. Fill the first measure with four quarter notes

4. Drag and drop the 6/8 Timesig in the first measure

Result: the first staff is wrong. It seems to "clone" the position of the notes of the second staff.

5. Now, make Undo, followed by Redo:

Result: No changing in the first staff, but now the second staff is also wrong. It seems to clone the position of the notes of the "initial" first staff.

Additionnal notes: the results are correct if the clefs are the same with linked staves (two Treble clef etc.)
But it occurs elsewhere that in "My first score" (with same cause)

Example: Create a score for piano:

- Remove the second staff (bass clef) -> add a linked staff (bass clef). So, the same configuration (two differents clefs, linked staves, change time signature) is back, with the same wrong result.