Maybe a loose fitting connector, parasitic resistance & capacitance on the pcb traces, internal pullup, or the fact that the single pin is split into 3 separate servo, laser and motor connections (including MOSFET circuit) could add up to enough that he pin wasn't able to drive to the minimum 2.7V to properly propogate the ttl/pwm signal down the line?
Just guessing though.
It appears that the value is going to need to be between 1k and 4k7 anyway, based on preliminaries, so it's not very far off from the suggested value if anything? Not really sure.
Could also be affected by the kind of wire I used between mana + ttl, since I didn't get one with either purchase, I had to make one.