Thanks for the report, but this is expected behavior. Ordering is NOT preserved in the command line parsing and would be technically infeasible to make it work.

You have 2 options:

1) Specify a mac address attached to each relevant --network string. Like

--network bridge:foo,mac=12:34:56:78:90:12

an omitted mac= piece will randomly generate one

2) Continue to use old style options, but stick a --mac RANDOM after before any of the other --mac arguments.

Closing as NOTABUG