Video standards in General info for Edit ROM Features are initially blank #20
OK... looks like the root cause is that various ROMs believe NTSC is "required", but the UI isn't putting that option into the list as a selectable option. Not sure why that is, to be honest... I.e. why ROMs would have 'required' be the default. Need to revisit that.
When adding a new ROM, we will combine features. If the new ROM is unknown, it would "combine" the 'Tolerates' setting (default for most) with 'Enhances' for video standard support - which means 'Unknown'. However, the result is that the ORing of those together produces a 'required' value for the video standard, which does not make sense. To address existing behavior of saved ROM lists, coerce the read and and write operations on the Ntsc and Pal properties. Also, fix how flags are combined to prevent this escalation from happening with other features. Unfortunately, if there are bugged ROM files out there for things like JLP and other features, they will remain bugged until the user manually fixes them, or deletes / re-adds the ROM after getting this fix.