A release of Windows 10 test assembly is postponed once more. At this time, this is no bug in 16212 build. The reason is a serious error that disabled some cell phones during internal testing. It is happened during the night of 1 to 2 June 2017. The 16212.1001.rs_iot.170531-1800 build became accidentally available for all devices (PCs, smartphones, laptops) independently whether one is connected to Windows Insider or not.
PC users got off easy because 16212 assembly is just stable less than usual on a computer. However smartphone owners with 10 Mobile OS had worse. Any attempt to install a new build introduces devices into endless reboot cycle. One need to reflash his cell phone using Device Recovery Tool to solve a problem. MS pretty quickly stopped the dangerous assembly spread, but two more builds (rs_xbox and rs_devices) were published after that. Later, ones were removed.
According to MS officials, inappropriate builds mistakenly got into the engineering system, which controls the corresponding issues explanation for Windows Insider program participants. Now MS company is engaged in fixing the consequences, so there will be no new test builds this week.