Actually when I said you can use WRITEMODBUS to write to the PC it doesn't mean that the PLC would think that it has successfully written the data. In fact because the PLC did not receive the timely response from the PC server it consider the write to have failed and therefore STATUS(2) is set to 0 all the time. And by default the PLC will retry another two times to send WRITEMODBUS command since it failed to get the response in time.
However, the PC server may still receive the write from the PLC (it just didn't respond).
Note that SETSYSTEM 1,n actually works on COMM4 for Nano-10, but only support maximum of up to 3 x 0.15s wait time for each COMM channel 1 to 4:
SETSYSTEM 1,n
where n = WAIT CYCLES xx xx xx xx two bits per comm port
bit 0 & 1 for comm 1
bit 2 & 3 for comm 2
bit 4 & 5 for comm 3
bit 6 & 7 for comm 4
00 = wait 0.15s for response
01 = wait 0.30s for response
10 = wait 0.45s for response
11 = wait 0.6s for response
So if you want to extend the wait time for READMODBUS via COMM4, run SETSYSTEM 1, &HC0 and the wait time will be extended to 0.6s which is the maximum supported wait time.