I got a response from the product manager for Rotatrim. Thank you Jon for suggesting I contact him, he was indeed helpful. Here's the response.
Thank you for your email with regard to your Rotatrim Professional trimmer. While I am extremely pleased that your existing Professional M24 trimmer has given you 10+ years of excellent service and I am sure it will continue to do so, I am disappointed that you have felt that there is an issue with the Professional M36 that you purchased.
You are correct that the clamp strip is set slightly back from the edge of the flat (counter) blade, this is by design and is to ensure that the clamp strip is not moved into the path of the cutting wheel which could subsequently cause damage when a cut is made. The clampstrip was never intended to be used as a guide to trimming, its purpose is to both clamp the material in place during the cut and also provides a path for the cutting wheel's rubber roller to run along allowing the turning motion needed to make the cut.
The gap between the edge of the flat blade and the clampstrip should be around 1/16" (1.6mm) and not 1/8" (3.2mm) as seems to be the case with the M36 that you purchased. It is possible that the clampstrip on the machine that you purchased had bowed and as such was sitting further from the edge of the flat blade towards the middle of the machine. I know that you have now returned the machine but can you recall if the distance between the edge of the flat blade and the clampstrip was consistent across the machine or was larger greater the middle of the machine?
As a result of your email I had a look at the "Luminous Landscapes" forum, on which there were some comments on the rule going out of square, this can happen over time and with prolonged use, however the design of the machine makes this very easy to rectify. Just in case you should face this issue with your existing M24 trimmer, I have attached a set of instructions on squaring the rule.
I am also extremely surprised that you did not receive a response from our distributor Manfrotto as they usually offer excellent customer service and did actually contact one of my colleagues following your email to them, to which he responded in line with the content of this email. I will contact Manfrotto to enquire as to why this enquiry was not followed up to their usual high standards.
It is possible that the DigiTech+ or the Technical series of machines may resolve the issue, as the clamp strip is of a completely different design. However, there must still be a gap between the edge of the flat blade and the edge of the clampstrip for the same reasons outlined above.
To summarise: -
There does have to be a gap between the edge of the flat blade and the clampstrip, such that the clampstrip is not damaged during the cutting process.
The clampstrip was not designed as a cutting guide, however we do understand that on your older machine as it was closer to the edge, you were able to use it as a such.
It would seem that the gap on the M36 you purchased may have been larger than we would normally expect, maybe due to the clampstrip bowing.
It is likely that another M36 machine would not have such a large gap between the clampstrip and edge of the flat blade.
I trust that this addresses your concerns with the M36 and the differences that you saw between that machine and the M24 that you have had for sometime. If there is any way in which I can further assist you then please feel free to contact me, at any time.