A 0 clearance insert should support the back of a cut preventing blowouts, thr original had a giant gap.
I consider this part to be semi consumable and will replace it in time. Having fitted it I needed to trim the front a little and will tune that before running off another.
I printed in PLA with a few extra radius's (5) and 20% infill but a block of 100% infill (10mm wide) slightly to the left of centre so the blade should go through that and not deal with any patterned infill.
https://www.einhell.co.uk/p/4300890-te-ms-18-210-li-solo/
The author marked this model as their own original creation.