Not many cassette multitracks that I know of were made that one could say had seamless punch-in. I’ve owned a couple Tascam portastudios that the punch-in/punch-out was virtually undetectable unless you isolated a channel, cranked it up and listened for the slightest change. Not sure about the MT8X. I don’t how well it was designed in that regard. However, there are a couple very important tips for punch-in generally speaking no matter what kind of tape deck.
The first is the benefit of demagnetizing (degaussing) the tape path. Any machine where this has been neglected can see an increase in popping and static type noises when the record circuit is engaged.
The other point has to do with punch-in technique. Even with a deck that is fairly quiet when punching in, the preferred technique in pop music (no pun) is to punch in on the beat of the kick drum to mask any noise. If some other type of music with low or no drums you can usually find a place to punch in where the attack of another instrument masks any popping.
The later generation decks I still own, whether cassette or open-reel, are virtually pop-free during punch-in, but I developed the habit of punching in on the beat from my early days, so I still do it that way.
