This is for information: I've bought an ASI294MC Pro back in August last year, and have had decent success with it from darker skies (Bortle 5 or better) - OSC from Tokyo however was really not giving me anything.
So after seeing tons of reports about how good the OPT Triad Ultra filter is (and how others use it without issue with the ASI294MC Pro), I bought it to use from Tokyo with my ASI294MC Pro.
But unfortunately, I found that all my images with the filter came out with a very pronounced X shape pattern across the whole sensor. It is from the sensor. And in multiple tests to identify the origin, I found the same issue with Astrodon HA and SII filters (but not OIII). So the sensor exhibits a X shape sensitivity unevenness in deep red wavelengths.
Unfortunately, while flats happily show the patter as well, it doesn't calibrate out properly. It calibrates out the light intensity, but the red cast is still there, even in calibrated frames (some examples here: https://drive.google..._4mqxSnaLkmq2PN). This means I have to use cropping and aggressive DBE to get anything out of the frame, which is extremely frustrating.
Upon discussing that with ZWO support, they told me the manufacturer of the sensor said that the issue is within tolerance, so that they will not repair or replace the camera under warranty.
Obviously this is very disappointing. Especially since others with the same camera and filter do not experience the issue.
So word of advice: if you have the ASI294MC Pro and want to use it with OPT Triad filter, first borrow an HA filter from someone and get some flats, see if you get a terrible pattern. If you do, well, don't buy the OPT Triad filter just yet...