When an RG should issue a DHCPv6 solicit

[Frank Bulk]

Should an RF issue a DHCPv6 solicit on its WAN interface only upon having
received an RA message with the RA bits marked "M"?  Or can/should it send
one out regardless?

We have a xPON vendor onsite to do some testing with their equipment in our
production IPv6 network and only one of the five RGs are working.  I suspect
it's because the RG's are waiting for that RA.

Any insight or pointers to RFCs would be appreciated.

Frank