we are facing database problem when we try to alter table by adding new column to a table. system prompt a message - index entry missing. how can we resolve this problem?

FYI, we had tried to export the data from that table and import again to new table and droping indexes & recreate but we facing data lost problem and the database seen like not stable. When we try to retrieve with difference arguments, some data is missing too.

Database version is sybase sql anywhere ver 5.5.04 build #1867