Do not remember the audio channel after reboot

OS: elementary OS 0.4.1 Loki
Problem: It cant remember which channel i choose for i adjustment volume.
Reproduce: You need at least 2 sound channels. Choose your, my is HDMI and S/PDIF (i dont use this one). Then make reboot from menu. Try to change volume, it would be (in my case) S/PDIF, but before restart i have used HDMI.
Before reboot:
After reboot:
Added: after long suspend time (8 hours), it again changed sound chanel from HDMI to S/PDIF.
Added: i make it default by manual by add this line to /etc/pulse/default.pa
set-default-sink output alsa_card.pci-0000_01_00.1

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Start by tracing how the sound plug selects and restores the default output across reboot and suspend, using the reported HDMI and S/PDIF setup as the reproduction case. Compare the plug's behavior with the manual /etc/pulse/default.pa setting and verify that the selected channel remains HDMI after reboot and after a long suspend.

Written by the indexing model from the issue text.