FWIW I used the M-series auto from 2008 through 2014 without problems. Using Encore software from Respirionics, I could see pressure changes and events, and the machine was effective for me. Data was stored on a smartcard and required a special reader to access, but I did that throughout my use of the machine. While your machine may have been defective or became that way over time, without looking at the data, how would you know? The M-series gave detailed efficacy data on non-responsive apnea, flow limitation, obstructive apnea, hypopnea, vibratory snores and leaks. It was not capable of providing detailed wave-form of flow and events which was possible with the PRS1 50 and 60 series, and Sleepyhead was never designed to import the smartcard data.
The old machines by Respironics and by Resmed only acquired the ability to wrote to SD cards starting about 2011 or 2012, but therapeutically, they worked very similarly to current machines. Keep in mind that more modern data storage and transfer methods like SD Bluetooth and wireless was intended to make data more available to clinicians. An unintended consequence was that it became more available to patients as well. To this day, manufacturer's consumer software is severely disabled to only show summary information and compliance information. The professional Encore and Resscan software was not intended for patient use, nor were clinician manuals supposed to be distributed to end-users. Forums like Apneaboard have made the software and manuals available by request, and the development of Sleepyhead by Mark Watkins in 2011 was very empowering. Prior to that, data was difficult to get and required expensive card readers and somewhat sophisticated computer ability, as well as access to software that was not publicly available. I recall spending $99 for the consumer version of EncoreViewer in 2008. What a rip-off!