I don't think I've ever encountered cross-hatching in any of the monitors I've come across (or at least I haven't regarded it as an issue), so I don't know how bad it can get.
But as a general rule:
If it's disturbing your everyday usage, then you might consider sending it back. But do note, manufacturer/seller probably won't accept it back as a "defect", so you might have to resort to DSR (if applicable). But on the other hand, if you indeed have to specifically "look for it", and if there's nothing else wrong with the monitor, then I'd suggest you keep it.
But as a general rule:
If it's disturbing your everyday usage, then you might consider sending it back. But do note, manufacturer/seller probably won't accept it back as a "defect", so you might have to resort to DSR (if applicable). But on the other hand, if you indeed have to specifically "look for it", and if there's nothing else wrong with the monitor, then I'd suggest you keep it.