PNG effect only applied in horizontal games

[ID4]

The problem is the following:

In my "mame.ini" configuration I have applied a PNG effect for all games, using the "effect" configuration parameter.

The png is applied in all games except vertical ones, when I run a vertical game this effect disappears.

In "mame.ini" I have the "rotate" parameter activated, to rotate the vertical games and play them in my horizontal monitor.

Curiously if I run a vertical game and from the mame menu the I rotate the game again (as if the game was horizontal) the png suddenly appears and is applied to the image.

This happens with version 273 of Groovymame, if I run official mame in the same folder with the same mame.ini, the PNG effect does not disappear when running a vertical game.

What could this be due to? 

Thanks in advance