This bug was found in both Beryllium master and in stable/lithium.

The SF selection algorithms dont appear to be working correctly
when concrete SFs/SFFs are specified in the SFP.

Here is an overview of the config

SFC:
[TcpProxy, TcpProxy, TcpProxy]

SFP hops:
SFF2->SF2
SFF1->SF1
SFF3->SF3

Im expecting these hops in the RSP:
RSP:
SFF2->SF2
SFF1->SF1
SFF3->SF3

With SF selection=RoundRobin, I get this:
RSP:
SFF1->SF3
SFF2->SF2
SFF3->SF1

With SF selection=Random, I get this:
RSP:
SFF1->SF3
SFF2->SF2
SFF3->SF3