So in order to fix this situation GUI will not offer you a proper way to do it. Therefore you have to do some typing by executing networker cli commands:
1. From the GUI (same can be done from cli, but it will not be mentioned here) take a note of the Volume name that have bogus expiration date
2. List the savesets that are suited on that volume by entering following cli command:
# mminfo -p -q "volume=volume_name"
From this list, take a note of the ssid number/name of the affecting saveset which have improper retention date.
3. Change the date of "bogus" saveset to corespond to your retention policy
# nsrmm -S ssid -e "mm/dd/yyyy 23:59:59" -w "mm/dd/yyyy 23:59:59"
Repeat this step if multiple savesets have bogus retention time.
At the end, when all savesets from that Volume have correct retention time, go back to GUI and check if problem with expiration date is solved. If not, repeat step #2 and check if you have missed some Save set with bogus retention time.