Same behaviour under xorg. 
I defined alternative shortcuts to forward and backward key on my MS keyboard.
backward switching works but forward switching only toggles between the last and the current.

Operating System: openSUSE Tumbleweed 20191118
KDE Plasma Version: 5.17.3
KDE Frameworks Version: 5.64.0
Qt Version: 5.13.1
Kernel Version: 5.3.11-1-default
OS Type: 64-bit
Processors: 4 × Intel® Core™ i5-4590 CPU @ 3.30GHz
Memory: 15,5 GiB

Can confirm this on current Plasma from master branch.

Operating System: openSUSE Tumbleweed 20200818
KDE Plasma Version: 5.19.80
KDE Frameworks Version: 5.74.0
Qt Version: 5.15.0
Kernel Version: 5.8.0-1-default

Actually, the current Activity switcher on master does not cycle with Meta+Q, it cycles with Meta+Tab.

I can confirm the same behaviour in the Task Switcher on Plasma 5.21.4, Frameworks 5.81.0 on X11 on OpenSUSE..

(I think this is the same bug):

With the plasma keyboard shortcut settings set to default, Meta+Tab is assigned to "Walk through activities".  

In an X11 session Meta+Tab displays the activity switcher panel and walks through all activities (as expected). 

In a Wayland session Meta+Tab does not show the panel and only cycles between the most recent two activities.  Meta+Shift+Tab cycles backwards through all activities (but still doesn't show the panel in Wayland)

Operating System: KDE neon 5.22
KDE Plasma Version: 5.22.2
KDE Frameworks Version: 5.83.0
Qt Version: 5.15.3
Kernel Version: 5.8.0-59-generic (64-bit)
Graphics Platform: Wayland
Processors: 2 × AMD A6-6400K APU with Radeon(tm) HD Graphics
Memory: 7.7 GiB of RAM
Graphics Processor: AMD CEDAR

The activity switcher behavior is still very much broken under Wayland - I think all these issues are related, but I can't be sure:

When using the "Walk through activities" shortcut by holding the modifiers (I use a non-default and more complex shortcut with multiple modifiers) and hitting the activation key repeatedly, the following behaviors can be observed - with no discernible reason as to which behavior is happening:
- switcher moves to next activity as expected.
- switcher cycles back and forth through only two activities (when there are more).
- switcher appears to try to switch to the next activity (the selector in the activities bar jumps to the next activity and wallpaper changes briefly) but then immediately goes back to the current one.

Sometimes hitting the activation key quickly multiple times can coax one of the other behaviors to appear, though for me the last one is the most consistent.

Just updated to 5.23 and the Activity Switcher adds an entry to task manager sometimes when I switch activities in quick successions with some windows open in all activities. This happens both in X and Wayland. 

In addition to it, on Wayland, the switcher behaves like a window and shifts the windows already open instead of overlapping the windows.

(In reply to Shavez from comment #7)
> Just updated to 5.23 and the Activity Switcher adds an entry to task manager
> sometimes when I switch activities in quick successions with some windows
> open in all activities. This happens both in X and Wayland. 

Huh! I was wandering what that new window, labeled "Plasma" with zero width, that started appearing recently. I didn't tie it to the activity switcher, but it looks like you are right - if I switch activities back and forth using the "Walk through activities" shortcut, I can see a new task manager entry labeled "Plasma" that disappears after a few seconds - and sometimes it doesn't disappear but remains until I close it with the taskbar context menu. This may warrant opening a new ticket?

(In reply to Oded Arbel from comment #8)

> This may warrant opening a new ticket?

I guess you are right. I will open a new ticket.

(In reply to Oded Arbel from comment #8)
> (In reply to Shavez from comment #7)
> > Just updated to 5.23 and the Activity Switcher adds an entry to task manager
> > sometimes when I switch activities in quick successions with some windows
> > open in all activities. This happens both in X and Wayland. 
> 
> Huh! I was wandering what that new window, labeled "Plasma" with zero width,
> that started appearing recently. I didn't tie it to the activity switcher,
> but it looks like you are right - if I switch activities back and forth
> using the "Walk through activities" shortcut, I can see a new task manager
> entry labeled "Plasma" that disappears after a few seconds - and sometimes
> it doesn't disappear but remains until I close it with the taskbar context
> menu. This may warrant opening a new ticket?

https://bugs.kde.org/show_bug.cgi?id=443941

Opened a new ticket.

Hello,

I am not sure if this is the same issue as I would like to report. I am on X11, not wayland. 

Currently I have configured 3 activities and the following shortcuts:
ctrl+alt+down => Walk through activities
ctrl+alt+up => Walk through activities (Reverse)

While the (Reverse) case correctly cycles through all 3 activities, the down-hotkey only switches to two of them.

Operating System: Kubuntu 21.10
KDE Plasma Version: 5.23.3
KDE Frameworks Version: 5.88.0
Qt Version: 5.15.2
Kernel Version: 5.13.0-21-generic (64-bit)
Graphics Platform: X11

I have found that I do not want to use
"Walk through activities" and "...(Reverse)"

but instead
"Switch to Next Activity" and "Switch to Previous Activity". 
This does what I want when pressing ctrl+alt+Cursor-Up/Down

Though I am not sure if the Walk Through actions should not reach all activities, too.

Git commit f4a2161017b831c91a532c6a1dfa5c40da423ef5 by Ben Cooksley, on behalf of David Redondo.
Committed on 16/12/2021 at 17:15.
Pushed by ngraham into branch 'master'.

switcherbackend: only map the workaround window once the switch is complete

Otherwise we will switch first to the new activity, but activating a new
window on the old activity will cause a switch back.

M  +5    -2    imports/activitymanager/switcherbackend.cpp

https://invent.kde.org/plasma/plasma-desktop/commit/f4a2161017b831c91a532c6a1dfa5c40da423ef5