When I use the same cell from a DGNLIB to pattern with it displays different compared to existing DGN files despite using the same tool settings at time of placement.
In addition if I place the same pattern to a new element in an existing DGN file with the same tool settings, it will displays the same as other patterned elements within the file.
The pattern cell's graphics within the DGNLIB had been modified whilst retaining the same name.
Thus the shared cells definition used for patterning resides in the existing DGN file, so when placed again it uses that definition rather than the new definition from the attached DGNLIB. For new DGN's where the pattern had not been placed previously obtains its definition from the attached DGNLIB.
To resolve the cells graphics within the DGNLIB should be modified to reflect the same definition prior to modification. Some suggestions :-
Restore the DGNLIB from a backup if one exists.
Open the DGNLIB and modify the models graphics to previous state.
(If unsure of the exact original definition of the cell, open an existing DGN file, in the Cell Library dialog turn on the Shared Cell checkbox then locate and place into the file. Drop the place shared cell to graphics using the Drop Element tool, the cell can then be recreated using these graphics)