Reassigned Multimedia Keys do default action on first use

[Photonik]

(using v 3.5.8698, Win10)

I'm using MusicBee mainly for audiobooks, so skipping to the next track isn't what I need/want. I instead reassigned the prev./next multimedia keys on my keyboard
Key: MediaPreviousTrack (Global:yes) to Playback: Skip back 20 seconds
Key: MediaNextTrack (Global:yes) to Playback: Skip forward 20 seconds
(Global Yes/No has no effect on the issue either way)

This works fine in general, but I noticed that on first start of the program, the first time I hit a multimedia key, it'll perform the default action.
So in case of the prev./next key it'll skip to the previous/next track/chapter, instead of the 20 seconds, how I configured it.

It is specifically the first time A multimedia key is pressed. If I start the program, then start playback by pressing the physical play key on my keyboard, all other MM-keys will work fine afterwards. If I start playback by pressing the virtual play key in the program and the prev./next key is the first physical key I press, it'll skip the track/chapter and only after that it'll skip the 20 seconds as assigned. This happens on every program start.

This issue does not happen with regular keys. I tried assigning the skip fwd. 20 seconds to the space bar and this works without issues as first use. If I then press the prev.-multimedia key to skip back after it (so first MM-key use), it'll still skip back a chapter the first time, then the assigned 20 seconds. So this is an issue with (re)assigning multimedia keys, not just with any keys.

In short: First multimedia key press bad, all following are fine.

My guess would be, that the reassigned multimedia keys aren't registered at program start, but after they are used the first time, or something in that direction, I don't know.
The keyboard is a basic Cherry G230, standard US-Intl. layout with six MM-keys, so there's no special software running for it that could interefere. (although Logitech Gaming Software 9.04.49 is running for the mouse)

Hope you can have a look at it.

Dominik