Sharp PC-E500 to PC link issues

[fy789]

I contacted the staff at the manufacturer, tmfg.jp, and after multiple rounds of correspondence, apparently they forgot to program the logic
inversion of the 4 flow-control signals. They send me the instructions to do the flash programming and it works afterwards.

Now, I can use "LOAD" without any issue afterwards for transferring a BASIC games into the E500S successfully. (ASCII file)

Thanks to all who tried to help!