I'm afraid you're not providing enough information to really figure it out, but if this is the minimOSD type boards you're talking about, those are a bit finicky to setup and a lot of problems are based on either the software or the power setup... if you describe your components, what version is installed, and how they're connected, that might help.
Otherwise, all we can really say is to check the software setup, and check the power hookup.
If you mean "infrared" -- are you saying the camera only works in low light situations and when it's daylight or too bright, the colors are washed out / wrong? It could be the infrared film / filter on the camera fell off or was removed. That's a function of the camera, and not the OSD. It's usually either a tiny thin film between the lens and the sensor, or it could be a coating on the lens as well, I suppose.
I wouldn't necessarily call it unreliable, but it requires a lot of setup. Setup in software and hardware. Given what you describe, my guess is that it's still one of two areas for you to look into: the software setup AND/OR the power setup.
For power: There are two types of minimOSD's, the original has a digital (the telemetry input side) and analog (the video input/output) side. The digital side required 5V and the analog side required 12V. If you have a newer/modified version that gets rid of the 12V side power requirement (usually by skipping the built-in buck/linear converter) you can save on some heat and wiring complexity (assuming your FPV gear is also all 5V). Anyway, I think a lot of problems stem from this complexity. So, the question remains, which version is yours?
For software: oh where to start? First off, there are multiple software that will work on minimOSD. Probably the two most popular ones I'm familiar with are:
If I'm not mistaken, I think most minimOSD hardware, if they come flashed with any software, default to the minimosd-extra software, which hasn't been updated in years, but I do know does work (I have 2 APM based aircraft that use this software). I have one minimOSD board setup with the scarab-osd (not the latest version, but pretty recent / within 1 year or so) that's setup for a F3 FC running betaflight (not the latest).
Anyway, as you can see, there are many other options in terms of software and flight controller integration... so, again, more details are needed.
Heh, I think the only way you could have the camera and osd wired to different grounds would be if one of them didn't have the ground wire connected. All your components, if their ground wires are connected should all end up on the battery ground.
I have them wired into a pdb with that circuitry that prevents them from interfering which each other as long as they're on different pads. I hope it is sufficient. If not please tell me. I have bypassed the osd and I'm all good now. @PhyBorg What do you mean by twisting the +- wiers? Does that cancel out the interference waves?
Basically any syraight wire is an antenna. When electronics are placed in close proximity that transmit radio waves these wires can capture some of that signal radiation.
By twisting the wires it limits the area for those signals to be introduced. Further more the ground becomes a natural path as energy flows positive to negative. The ground wire wrapped around the others forms a cage and directs those signals to ground.
As for camera to vtx the shortest paths for signal is best. With newer pdbs where voltage regulators and filters are added that direct path becomes broken.
By putting the ground wires on one pad that restores a direct path yet still allows the circuits to do their thing on the positive side.
Its not the end all to signal issues but does solve most of the common problems.