Chances are you have already come across this problem, and chances are you found out the solution. But this one can be a real puzzler and is too vital to omit.
Have you ever xreffed in a drawing, made lots of tweaks to the layer properties of the xref, only to find that after closing and reopening the drawing all your tweaks were lost!?
Well, there’s a system variable called VISRETAIN, which controls this behaviour.
Setting to VISRETAIN to 0:
The layer table, as stored in the reference drawing (xref), takes precedence. Changes made to xref-dependent layers in the current drawing are valid in the current session only and are not saved with the drawing. When the current drawing is reopened, the layer table is reloaded from the reference drawing, and the current drawing reflects all of those layer property settings.
Setting VISRETAIN to 1:
Xref-dependent layer changes made in the current drawing take precedence. Layer settings are saved with the current drawing’s layer table and persist from session to session.
I hope this helps!