two way tcp retransmissions

Od thing I'm catching today. The tcpdump shows such sequence for any incoming traffic for several VIPs in my environment:

IP Source -> IP VIP : SYN

IP VIP -> IP source : SYN, ACK

IP Source -> IP VIP : TCP Retransmission (SYN)
IP VIP -> IP source : TCP Retransmission (SYN, ACK)
IP Source -> IP VIP : TCP Retransmission (SYN)
IP VIP -> IP source : TCP Retransmission (SYN, ACK)
IP VIP -> IP source : TCP Retransmission (SYN, ACK)

The retransmissions are not always in that order, sometimes they just go out from VIP. Any ideas what might be causing them? I've checked the firewall in the path, and nothing seems out of order. The packets are going through this path:

Internet -> Akamai -> FW -> F5 -> webservers

I have no idea what Akamai is doing here, but it seems like test packet that went around it followed the same behaviour. The traffic obviously never reaches the webservers, as the handshake is not being finished on F5

Any tips?