xscreensaver won't let me unlock on resume from hibernate


While unlocking after resuming from suspend to RAM works fine & as expected, when I resume from suspend to disk, I see the unlock screen quickly flashing up for a moment before the screen turns black again and even entering my password on the blacj sreen, won't unlock my desktop. This is on my old ASUS Zenbook UX32A laptop.
I'm not even exactly sure how to troubleshoot this. It may have nothing to do with Xscreensaver but with resuming from hibernation. Any ideas?

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