Official comment
If you go to your preferences and disable DVS mode, that button will disappear and the software will be forced to INT mode.
In rekordbox 4.2.1 i can only set another tempo range on deck 2.
There is also only the cue button available on deck 2.

I completely reinstalled rekordbox, but it doesn't help.
If you go to your preferences and disable DVS mode, that button will disappear and the software will be forced to INT mode.
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Sorry to hear about this issue.
Would you try to press "INT> button" on deck 1/3/4?
If it does'nt help, would you try to uncheck "Preference -> DVS -> checkbox(Enable DVS Function)"?
Thanks, this was the solution for me.
But I do not understand, why only deck 2 works with enabled DVS function.
Can tell me?
What hardware are you using?
DDJ RZX, but it doesn't matter if the controller is connected or not.
@Chris
Cue button & Tempo slider aren't available in RELATIVE or ABSOLUTE MODE.
Cue button & Tempo slider are available in INTERNAL MODE.
In your case , Cue button & Tempo slider aren't available in INTERNAL MODE.
So this is a software bug. Sorry.
①Wourd you press "Int>" Button ( in red circle ) on deck 1 / 3 / 4 with enabled DVS function?
If you press "Int>" button, DVS MODE will change to INTERNAL MODE.
②If it does'nt help, would you press "DVS MODE" Button (in yellow circle ) several times with enabled DVS function?
If you press "DVS MODE" button, DVS MODE will toggle between RELATIVE MODE & INTERNAL MODE. ( REL -> INT -> REL -> INT -> .....)

Point 1 doesn't work, the point 2 was the solution for me.