Here is a simplified version of the trace:
11:26:46.095783 - Client:54403 > VIP:8081: SYN
11:26:46.095802 - VIP:8081 > Client:54403: SYN ACK
11:26:46.096034 - Client:54403 > VIP:8081: . ACK
11:26:46.096252 - SNAT:54403 > Node:8081: SYN
11:26:46.096317 - Client:54403 > VIP:8081: PSH ACK
11:26:46.195878 - VIP:8081 > Client:54403: . ACK
11:26:47.096001 - SNAT:54403 > Node:8081: SYN
11:26:48.296162 - SNAT:54403 > Node:8081: SYN
11:26:49.496319 - SNAT:54403 > Node:8081: SYN
11:26:50.695996 - VIP:8081 > Client:54403: R ACK
11:26:51.698644 - Client.54408 > VIP:8081: SYN
11:26:51.698663 - VIP:8081 > Client.54408: SYN ACK
11:26:51.699132 - Client.54408 > VIP:8081: . ACK
11:26:51.699335 - SNAT:54408 > Node:8081: SYN
11:26:51.699341 - Client.54408 > VIP:8081: PSH ACK
11:26:51.798994 - VIP:8081 > Client.54408: . ACK
You can see that the node never responds to the SNAT address to estabblish a TCP connection. If you capture a trace on the node, do you see the response going out a different interface?
If you try the same test with SNAT automap, LTM should use a self IP on the node's subnet and the response should be sent back to LTM on the same interface the node received the request on. I'm surprised that SNAT automap wouldn't work here.
Aaron