Raid 5 is down after successful rebuild (replaced the drive)

The disks look synced in mdstat.log

md127 : active raid5 sda3[0] sdc3[3] sdb3[4]
      7804333568 blocks super 1.2 level 5, 64k chunk, algorithm 2 [3/3] [UUU]
      bitmap: 1/30 pages [4KB], 65536KB chunk

Also, volume.log shows the resync completed in about 12 hours:

data        disk test  2020-09-16 00:08:35  2020-09-16 08:07:37  fail       Channel=2 Model=WDC_WD40EFRX-68WT0N0 Serial=WD-WCC4E2SUK42Z     
data        resilver   2020-11-10 23:42:21  2020-11-10 23:43:33  degraded                                                                   
data        resilver   2020-11-15 15:18:11  2020-11-16 03:37:19  completed     

Does the volume tab show that the volume is redundant?

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Hans-Jakob wrote:

but the raid 5 button on the right hand side is not on (X-RAID).

If you are talking about the X-RAID control, then X-RAID is enabled if there is a green stripe on the control.  

If X-RAID isn't enabled, then it is safe to try to enable it.  That won't trigger any RAID sync activity (and that is already finished).

I redacted your log links.  Logs shouldn't be posted publicly (there is some privacy leakage when you to that).