Time selection dialogs like in the "Black", "Fade to black" and "Fade" plugins which use diaElemTimeStamp show an ampersand "&" instead of transforming an underscore in the title into an accelerator. Methinks this were a recent regression.
Fixed by [Qt] Fix & in timestamp widget (https://github.com/mean00/avidemux2/commit/59882c77c409dc5d9160eb17dcc128fd5f40eef3), thx.