Normal version, not wide screen. Thus far the load issue seems to effect specifically omni designs that I composed in SSW 0.6.83.1.
Specific designs that won't load include the Avalanche, Doloire, Ryoken III XP, Sarath, Tenshi, and Thor II. Omni's made with the same version of SSW that do open correctly include the Vulture MK VI, Mad Cat MK VI, Wendigo, Templar III.
I can go into SSW 0.6.83.1 and open or load up any of those mechs that are causing me issues in and they are just fine. It is only when I try and open or load from a default status in 0.7.3.20191126 that nothing loads. If I am in another mech/omni file, lets say Mech X, and opening or loading one of these 'problem' mechs then the mech file for Mech X will remain and the selected variant drop down at the top of the screen will grey out with whatever version of omni I started in.
If you need any further details let me know.