Rectoverb 25 : Fade/gap problem when switching channels

Hello,
I've got a very annoying fade/gap when I switch channels. It's quick, but it kills all my first attacks.
Never experienced anything like this with my others amps.
I've made a recording, it's clearly visible in the soundwave. Even when playing quick notes, switching will create a "silence" followed by a quick fade.

While I've found some people complaining about "pop/fade" with old amps, I haven't found users of Rectoverb 25 that complain about that.

I'm wondering, is there a problem with mine, or is it a common problem for this model (I hope not!) ?

Thanks in advance !

I know switching through the channels a couple times before playing seems to help the popping, does that help the fade problem you experience?

Thanks for your answer !
I've just tried, but no change at all.