Sequential circuits samplers

Hi. A problem which occured recently was that the envelope "hangs". That occur when I try to make an envelope that has a longer sustain. The sound continue to sustain and never ends. I can only stop it by either press a key 8 times or turn off the machine. But strangely, the envelope works fine for sounds in reverse mode. Any idea of what can be wrong and how to fix it?

Thanks for all help
//HL