this fix also applies to other games where white box's / lines appear, as they are usually just transparency issues. one such example is the cutscenes in the Evangelion game where the scene fades in but leaves a garbled mess
edit.
a good tip to note is that having press r to reset clock enabled in the cheat box will cause the game to freeze when you go to change pokemon in certain modes.
what is strange clements is that before just now i have never seen those issues in pokemon stadium. all my battles looked fine.

just noticed something else :O
edit, fixed.
the colors for the bg's in the intro are broken in the Dx8 plugin but show properly in the Dx6 plugin.
ok differences between plugins
Jabo Dx6 1.5.2 = renders most correcly but prone to black artifacts on surfaces such as the ground.
Jabo Dx8 1.6 = Requires d3d clear mode set to perframe to remove white borders, and requires use legacy pixel pipeline to correct the colours in the cutscenes and all looks fine.
note.
D3D clear mode must be reset to default when choosing the match pokemon, and legacy pixel pipeline breaks water in the background.