There is a WLAN connection problem if DHCP is disabled since the last two releases (24th and 26th of Feb) on Ultimo 4K. The problem is that after each restart of the box, the DNS is reset to 0.0.0.0. and you'll have to enter it each time manually again and again if you want internet working. If DHCP is enabled all is OK.
So, if manual network settings are set, the connection is OK, but no internet unless you enter manually the DNS. Then all is OK until you restart the box. After the restart, it shows the box is connected, but due to DNS reset to 0.0.0.0. no internet until you enter it again. Hope somebody can test and confirm if can reproduce the bug and apply fix for it.