I would be very surprised if your injectors are stuck open. I wouldn't worry to much about continuity readings of injectors. All you have there is a coil which lifts the pressure off the springs which allows fuel through.
At the sake of repeating myself, does the engine ?un ok now?
There is a manufacturing problem with those injecto?s which causes 'cavitation erosion' of the nozzle tips causing excessive fueling leading to more frequent regens. Just because a DPF is regening frequently doesn't mean there is a problem with the DPF and it needs removing and ultrasonically cleaning or àll manner of expensive sensors need changing. No, the problem is in worn nozzle holes. Most dealers are not awàre of the problem and Mazda don't inform them of the symptoms, nor do any sensors.
I went through this problem during Covid and Mazda tried all sorts of excuses to blame the driver because the car wasn't been run on ?ong journeys, but it wouldn't have made any difference. Òne muppet said it was moisture trapped in the cylinders causing rusting, complete load of hogwash.
This problem shows up by a distinct change in fuel consumption, sump level rising above the max line within 3k miles, frequent regens with the frequency increasing. Yet the strange thing is the car runs we and sounds good.
Your previous problem of worn camshaft is becaue of incorrect heat treatment of cams and followers another known problem by Mazda, but they are not proactive but leave you to report it , hopefully outside of the warranty period. The other known problem, particularly with early cars is leaking injector pockets , the exhaust gasses contaminating the lube oil and causing blockage of suction filter and the wiping of the bearings.
It seems to be the practice these days that as soon as a problem develops with a car the owner sells it, says nothing about problems and nor do dealers and a FSH is hardly worth the paper its written on as it doesn't cover any failures.
Changing injectors is not cheap, looking at old injector nozzle hole is difficult as they are so small and you need a new injector side by side to compare the nozzle hole diameters.
I took photographs of mine but even fully blown up pior to pixilation and using a Dslr its still difficult to see.
Changing the injectors for new Mazda supplied ones you see vast improvement in fuel consumption and a distinct drop in oil contamination if Forscan is used to monitor the figures on a regular basis.
Every car I have owned I have kept a book on fuel consumption from day 1 as its the best way of telling you how the engine is performing. Plot the figure every time you fill up from a 1/4 tank on a graph, after a year take a year average and start another graph showing Max,Min, Median and average from new and if there is a problem then the changes can be seen on both graphs, over a year and over several years.