I can confirm the same issue on a DS-213j and on a DS-216play.
TL;DR:
Two devices, same issue. The issue exists at least since DSM 6.2.4-25426 Update 3.
DS-213j:
- Several updates done on March 31: File Station, Synology Drive Server, Universal Search, VPN Server (see screenshot). And even if it's not part of the logs, I'm pretty sure that the update to DSM 6.2.4-25556 was done that day as well.
- No other settings have been changed before or after that day.
- Since then, no more "Internal disks woke up from hibernation" entries are visible in the logs and whenever I check the device itself, I can hear the disks are spinning
- USB disk hibernation still works fine, my USB drive wakes up every night for my backup job
- Current DSM version is DSM 6.2.4-25556 as of today
DS-216play:
- Several updates done on April 6: Synology Drive Server, Universal Search, WebDAV Server, File Station, Speicher-Analysator, Node.js, VPN Server, OAuth Service (see screenshot). And even if it's not part of the logs, I think that DSM 6.2.4-25426 Update 3 (
caution: that's even an earlier version as above!) was installed that day. See below why I'm sure about that.
- No other settings have been changed before or after that day.
- I have realized the issue already on May 10. On that day, I installed DSM 6.2.4-25556 Update 1 (the one this thread is about). Before, DSM 6.2.3-25426 Update 3 was installed. I'm 100% sure about both versions because I noted them down before and after doing the update.
- The update brought no improvements unfortunately. When searching for "hibernation" in the logs, you can see that it stopped doing that on April 6 (see screenshot). You can also see that I've played around with the hibernation time, which also had no effect.
Any suggestions?
EDIT: Oh, and yes, I have read
this article 