Problems with particle filters

Hello, I have been driving a Saab 93 Sport Kombi 1.9TiD (Vevtor) since November 2005. I am really very satisfied, had previously Volvo V70. However, right at the beginning a problem occurred which could not even fix my contract workshop and I would like to describe briefly here, in the hope that someone has observed/experienced this and can give me a hint. Although the particle filter does not regenerate properly, or only insufficiently, if you drive shorter distances often, w As for me, this is often the case. So the statement of the workshop. As soon as the regeneration of the filter drops below 30%, the engine switches to a “schoning program”, which completely shuts off the engine. It no longer has any power and does not even come over 90km/h. So far I always had to take the way to the workshop, which shrugged with the software picked up the engine lock again and then ran the engine for 10 minutes with 4000 revolutions in order to carry out the regeneration. I have to do 4 times now. According to my observations, the Phenomen occurs especially when I drive to the Becker, have breakfast at home, and then use the car again after a long time, after it is completely cold again. Just at this moment, the engine lock turns on, and the nice “engine damage” lamp lights up. As I said, the workshop does not know any advice. I don’t want to take this condition any longer and therefore am on the search e after the cause. Opel has no problems with its filters, as far as I could find out. Can someone help me further? Or do you have a tip? Thank you in advance for any constructive answer LG, Vurt