Once again – apologies to sound like a broken disc 😀 – it’s not really fault of the OSSC’s bob deinterlace per se, and it doesn’t randomly happen with ‘certain types of panels’.
This is a known issue, at this point, and it’s quite surprising to me how this piece of information – as empirical and ever evolving as it gets – is still buried in several threads on various forums (SHMUPS, here at VGP too…), instead of being brought up and stuck on top of dedicated boards, to everyone’s attention.
Basically, to this very day, it’s been proven how IPS displays – from many manifacturers, such as LG, HP and ViewSonic – are more or less sensitive to severe screen flicker (which is that constant shimmering effect you get on screen, when you display interlaced sources, like your PS2 480i games), which produces the temporary burn-in/after-flicker mask you experienced and pictured. Not enough tests have been made on VA panels, in order to realistically establish how they behave, while TN monitors appear to be immune to all that.
Also, it may have made it a bit worse, but the fact you paused the game most likely didn’t make a huge difference: I personally observed the same result – on an LG 4K monitor – after playing Virtua Fighter 2 on my SEGA Saturn for about 10 minutes, with no pauses. Some PS2 games (Ridge Racer V) marked the screen after an even shorter time.