Not sure how to describe the “deinterlacing”, pretty sure deinterlace was off in OBS but something was having trouble with static lines (i.e. menus). It wasn’t a steady flicker, it’d just wiggle a bit every now and then. Possibly related to noise on my BNC>VGA cable. Still haven’t been able to poke at the settings for that yet.
I’ve also had issues with the OSSC not sending out a signal when I first start it? Usually happens when the console is turned on before the OSSC. I’ll get the test pattern on OSSC startup and it will say it’s synced to a signal, but I get a black screen (capture card)/no output (monitor, goes into standby). This is usually solved with unplugging/replugging the A/V cable or restarting the console and then changing the scaling options around. Going to pick up a HDMI splitter so I can monitor the OSSC output easily and completely remove the capture card from the equation.
In addition to that, sometimes the OSSC will drop sync during 240p/480i resolution changes. Typically the screen will rapidly switch between saying 260p and 525i, and this is resolved by changing the scaling settings. Sometimes the scaling options (typically 1x and 3x?) will do this when you set to them. Sometimes not.
Again I still need to sit down and figure out the exact behavior, but generally speaking this seems to be a bit more finicky than I was expecting. I do wonder how many of these issues are cable related, and not being able to use my SCART cable isn’t helping. Sounds like I might just have to contact support about that.