Ultra 6 Plus - freezing after upgrade from 4.2.31 to 6.x

StephenB Thank you

I am on 6.10.6

I understand regarding the downgrade, I see 6.9.3 here https://kb.netgear.com/000055199/ReadyNAS-OS-6-Software-Version-6-9-3

Should I downgrade directly to that version? Or I should try going backwards to 6.10.6, 6.10.5, 6.10.4 etc

I did check the logs (I am still finding my way around there) - in the system.log I have the following before I rebooted the unit:

Jan 16 05:39:48 ReadyNASUltra6 dbus[2893]: [system] Activating service name='org.opensuse.Snapper' (using servicehelper)
Jan 16 05:39:48 ReadyNASUltra6 dbus[2893]: [system] Successfully activated service 'org.opensuse.Snapper'
Jan 16 05:41:07 ReadyNASUltra6 msmtpq[18154]: mail [ 1 ] [ 2022-01-15-18.27.46 ] from queue ; send failed ; msmtp rc = 76
Jan 16 05:41:09 ReadyNASUltra6 msmtpq[18197]: 2 more mails from queue failed to send with rc = 76
Jan 16 05:47:27 ReadyNASUltra6 connmand[2899]: ntp: adjust (slew): -0.000245 sec
Jan 16 05:51:10 ReadyNASUltra6 msmtpq[18324]: mail [ 1 ] [ 2022-01-15-18.27.46 ] from queue ; send failed ; msmtp rc = 76
Jan 16 05:51:11 ReadyNASUltra6 msmtpq[18367]: 2 more mails from queue failed to send with rc = 76
Jan 16 05:58:45 ReadyNASUltra6 mdadm[2890]: RebuildFinished event detected on md device /dev/md127, component device resync: mismatches found: 1518992896 (on raid level 5)
Jan 16 05:58:56 ReadyNASUltra6 msmtpq[18470]: mail for [ -C /etc/msmtprc @zzz@gmail.com,zzz@yahoo.com --timeout=60 ] : send was unsuccessful ; msmtp exit code was 76
Jan 16 05:58:56 ReadyNASUltra6 msmtpq[18472]: enqueued mail as : [ 2022-01-16-05.58.55 ] ( -C /etc/msmtprc @zzz@gmail.com,zzz@yahoo.com --timeout=60 )
Jan 16 06:01:22 ReadyNASUltra6 msmtpq[18524]: mail [ 1 ] [ 2022-01-15-18.27.46 ] from queue ; send failed ; msmtp rc = 76
Jan 16 06:01:24 ReadyNASUltra6 msmtpq[18587]: 3 more mails from queue failed to send with rc = 76
Jan 16 06:04:31 ReadyNASUltra6 connmand[2899]: ntp: adjust (slew): +0.000613 sec
Jan 16 06:11:25 ReadyNASUltra6 msmtpq[18700]: mail [ 1 ] [ 2022-01-15-18.27.46 ] from queue ; send failed ; msmtp rc = 76
Jan 16 06:11:26 ReadyNASUltra6 msmtpq[18763]: 3 more mails from queue failed to send with rc = 76
Jan 16 06:17:01 ReadyNASUltra6 CRON[18814]: pam_unix(cron:session): session opened for user root by (uid=0)
Jan 16 06:17:01 ReadyNASUltra6 CRON[18815]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly)
Jan 16 06:17:01 ReadyNASUltra6 CRON[18814]: pam_unix(cron:session): session closed for user root

-- Reboot --
Jan 16 13:03:52 ReadyNASUltra6 cron[2886]: (CRON) INFO (pidfile fd = 3)
Jan 16 13:03:52 ReadyNASUltra6 cron[2886]: (CRON) INFO (Running @reboot jobs)
Jan 16 13:03:52 ReadyNASUltra6 wsdd2[2887]: starting.

...

If I am reading this correctly, it froze at 6:17 AM - and I powered it off/restarted at 13:03

I did have another problem which I didn't mention before, because it shouldn't be tied to this freezing issue. I tried setting alerts with both gmail and yahoo addresses, it didn't work, it looks like both companies tightened up security (solutions I found in other threads didn't work for me). But I just configured it using another email account and was able to send a test.