spindle speed strange behavior with push buttons

I have external pendant cw ccw and stop pushbuttons connected to mesa 5i25+7i77.

First time after linuxcnc startupp if i hit cw button once speed is okay (min. speed 50rpm). If i hit cw once again reduce speed to 1rpm. Same behavior to ccw.

If i give some speed in mdi mode forexample s=100 and then try again spindle behaves normally

we need more information please , as to type of pendant , version of linuxcnc being used
and perhaps attach your config folder as an archive

What pin did you use?
How did you connect them?

Norbert