9.11.5rc1 statschannel test sometimes failing on ubuntu 18.04

in 9.11.5rc1, on ubuntu 18.04, the statschannel test sometimes fails. Testing 9.11.4-P2 on the same machine, I was unable to replicate the failure at all.

the failure seems to be rooted in the first check.

traffic.expect.1 (file included in tarball):

tcp request-size 16-31: 1
tcp response-size 64-79: 1

traffic.out.x1 (file generated by the test):

tcp request-size 16-31: 1
tcp response-size 16-31: 1

sample failure output:

S:statschannel:Wed Oct  3 12:10:33 PDT 2018
T:statschannel:1:A
A:statschannel:System test statschannel
I:statschannel:PORTRANGE:12100 - 12199
I:statschannel:JSON tests require JSON library; skipping
I:statschannel:fetching traffic size data (1)
I:statschannel:... using xml
traffic.out.x1 traffic.expect.1 differ: byte 45, line 2
I:statschannel:failed
I:statschannel:fetching traffic size data after small UDP query (2)
I:statschannel:... using xml
traffic.out.x2 traffic.expect.2 differ: byte 45, line 2
I:statschannel:failed
I:statschannel:fetching traffic size data after large UDP query (4)
I:statschannel:... using xml
traffic.out.x4 traffic.expect.4 differ: byte 45, line 2
I:statschannel:failed
I:statschannel:fetching traffic size data after small TCP query (5)
I:statschannel:... using xml
traffic.out.x5 traffic.expect.5 differ: byte 100, line 4
I:statschannel:failed
I:statschannel:fetching traffic size data after large TCP query (6)
I:statschannel:... using xml
traffic.out.x6 traffic.expect.6 differ: byte 100, line 4
I:statschannel:failed
I:statschannel:checking consistency between named.stats and xml/json (7)
I:statschannel:checking consistency between regular and compressed output (8)
I:statschannel:checking if compressed output is really compressed (9)
I:statschannel:exit status: 5
R:statschannel:FAIL
E:statschannel:Wed Oct  3 12:10:36 PDT 2018