I33 Errors - Source TS3410DN can't see target TS3410DN

[PaulGrace]

I have two TS3410DN next to each other, each connected by LAN1 to my LAN, 192.168.0.X and also connected to each other via LAN2 on 169.254.10.X for replication.

Replication was working fine last week (for a couple years), but this week my target has become invisible to my source.  I can see both TS3410 on my LAN and copy files between them, but replication just causes I33 errors.  I tried to PING the target drive from the Source drive using the utility in the "Network" page and it fails 100%

I would like to download the prior firmware to revert to pre 5.00-0.07 Firmware, but can't find the file on the website.

Alternatively, is it likely that the LAN2 interface failed on one of the two drives?

The log shows: repdaemon[11705]: rsync: [sender] failed to connect to 169.254.10.95 (169.254.10.95): Connection timed out (110) rsync error: error in socket IO (code 10) at clientserver.c(137) [sender=3.2.3]

[PaulGrace]

Update:

If I disable replication on the source, and restart the target, then I can ping the LAN2 & LAN1 target from the source, and ping the source from the target, and read/write files on the target across LAN1.
If I then enable replication, the source throws an I33 error, and the target LAN1 and LAN2 both stop responding, the target is no longer visible in Navigator, or by any machine on LAN1.

If I restart the target, delete all the source LAN2 replication links, and enter them all on the LAN1 interface, replication completes normally (but slower because of network traffic on LAN1)

It acts like replication over LAN2 breaks both LAN interfaces on the target, requiring a retstart, which returns at least LAN1 to normal, and at least ping works on LAN2 until it tries replication.

This does not seem like a hardware bug to me, because rebooting fixes it.

Does anyone have firmware from 2020?  Anything prior to 5.00?