How important is a Mokom Kavouah for Tefilla on a daily basis in the same Minyan (time wise) when a non member of the Shul – in a Shul where by the rules of membership there are non fixed seats but de-facto there are, always takes a seat that he knows and has been told is a Mokom Kavouah for a member of the Shul. That member feels that the lack of this availability to him has affected his Parnossoh and other issues in life.
Although Chazal state that having a fixed place in shul is important (and “one who does so, the G-d of Avraham comes to his assistance” – see Tur and Beis Yosef, Orach Chaim 90), this of course does not outweigh the concern of taking somebody’s seat.
As I understand the question, one person has paid for a seat, and somebody else sits in it, taking his fixed place against his – and this is surely wrong (the Taz treats the seats in a shul as regular “places of residence”).
The ‘squatter’ can surely fix his place in a different seat in the shul, and will both achieve the virtue of having a fixed place, and avoid taking somebody else’s seat.