It seems that the problem that I just posted under another topic where I was trying to run two instances of WSJT-X from two separate configurations is another instance of the JT4 decoding issue.  I tried running just the "Main" instance on its own, with JT4g as the set up mode from start up.  WSJT-X runs until the first attempt to decode then the Subprocess error comes up.

Details in the Subprocess error box says;

Running: C:\WSJT\RC1\wsjtx\bin\jt9 -s "WSJT-X - IC9700MainBand" -w 1 -m 3 -e C:\WSJT\RC1\wsjtx\bin -a "C:\Users\Owner\AppData\Local\WSJT-X - IC9700MainBand" -t "C:\Users\Owner\AppData\Local\Temp\WSJT-X - IC9700MainBand"
At line 13 of file C:\Users\bill\src\k1jt\wsjtx\lib\pctile.f90
Fortran runtime error: Index '-25' of dimension 1 of array 'tmp' below lower bound of 1

Error termination. Backtrace:

Could not print backtrace: libbacktrace could not find executable to open
#0  0xffffffff
#1  0xffffffff
#2  0xffffffff
#3  0xffffffff
#4  0xffffffff
#5  0xffffffff
#6  0xffffffff
#7  0xffffffff
#8  0xffffffff
#9  0xffffffff
#10  0xffffffff
#11  0xffffffff
#12  0xffffffff
#13  0xffffffff
#14  0xffffffff
#15  0xffffffff

If I run WSJT-X in another mode it seems to be OK.

Screen print below of single instance of WSJT-X with JT4g as start-up mode - Cheers - Dave (G0DJA)