I've spent the past couple weeks chasing down details on issues with United being unable to book some awards on SQ metal. I wanted to fly LAX-NRT-SIN on SQ and the coach seats appeared to be available to ANA, AV and AC; surely that meant I should be able to call and book them with an agent. Except not so much. And so I started to fear the return of StarNet blocking. After much back and forth and digging (including some help from more senior people there, not just res agents) the bug in the systems has been identified. It is not a willful blocking of the seats (i.e. NOT StarNet blocking) but it is a very real problem affecting all SQ flights which touch the USA (SQ1, SQ11, SQ15, SQ25 & SQ61). Those flights are not able to be booked - in whole or in part - as an award using UA miles at this time. They're working on solving the problem, but it isn't there yet. Added bonus: An agent confirmed that all awards involving SQ metal are now manually priced. Have fun with that.