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I have confirmed this behavior. You need to open a ticket with PTC so that they can file a SPR (bug report) for this issue and get it fixed.
In the meantime, you can manually change the session ID in the symbol.
IE:
&PTC_MASTER_MATERIAL
becomes
&PTC_MASTER_MATERIAL:2
where 2 is the session ID for the part in question. Session IDs can be turned on as a column in the assembly or they can be imported as a text file like discussed in this thread:
https://community.ptc.com/t5/3D-Part-Assembly-Design/Session-id/m-p/67624/highlight/true#M12248