A320 FMGS/IRU alignment issue

[767-300ER]

I have had this experience happen about 4-5 times in the last 6 months....

Turn IRUs to NAV
Go to INIT A page, insert flight number, and then city pair
Confirm ARP (aerodrome reference position) on Jepp 10-9 page
Press Align IRS button

Go back to INIT A page 5 or 10 minutes later, find that the ARP has reverted to the ARP of the previous flight, and the IRUs fail to align

Anyone else experience this? Is this a know issue?

Thanks in advance...