G76 -Somtimes- faults and does not synchronize

Usually Speed control loops use mainly FF0,P and I
(FF0 is adjusted for best open loop speed match with everything else 0
then P then I)

You can use an interactive HAL window.
Open a terminal and "halcmd -kf" to link to the HAL of the running LinuxCNC instance.

Then you can "setp pid.2.Igain 200" and such to change the PID settings on the fly.

These won't be saved to the INI, so make a note of the good settings then edit them in to the INI.

You can read (getp) or set (setp) any HAL pins you like from the command line.

show pin pid* - will show all pins matching the pattern.
loadusr halmeter
loadusr halscope - open some handy tools
exit - will quit the halcmd session.