SUCCESS!!!! I solved my problem.
After finding documentation on the SkyWatcher Protocol, I went back through the INDI debug log and tried to make sense of the state of each piece involved in the process. After looking over the commands and digging into the AstroEQ firmware source code, I finally discovered what has been causing the problem. When stopping the motors after a movement, the "GVal" is reset to a value of 0 by motorStopRA and motorStopDC, to "switch back to slew mode", except that the proper value for slew mode is 1 (at least according to the motionIsSlew(), motionIsGoto(), and motionIsLowSpeed() methods of AstroEQ.c). A value of 0 defines high-speed goto mode, which is being set when stopping the motor after the first movement. Then, because the :G command is not repeated by the INDI EQMod driver for movements in the same direction and at the same sidereal rate before the next :J command, the :J causes it to switch to high-speed.
Further down in the debug log I noticed this:
First Nudge:
"[MOUNT] StartMotor() : Axis = 2 "
"[COMM] dispatch_command: \":J2\", 4 bytes written "
"[COMM] read_eqmod: \"=\", 2 bytes read "
"[SCOPE] Compute local time: lst=10.38736394 (10:23:14.51) - julian date=2458362.30804270 "
"[COMM] dispatch_command: \":j1\", 4 bytes written "
"[COMM] read_eqmod: \"=E4377A\", 8 bytes read "
"[SCOPE] GetRAEncoder() = 8009700 "
"[COMM] dispatch_command: \":j2\", 4 bytes written "
"[COMM] read_eqmod: \"=264084\", 8 bytes read "
"[SCOPE] GetDEEncoder() = 8667174 "
"[SCOPE] Current encoders RA=8009700 DE=8667174 "
"[ALIGNMENT] Status: Mnt. Algnt. NORTH Date 2458362.308043 encoders RA=8009700 DE=8667174 Telescope RA 8.486128 DEC 89.600030 "
"[ALIGNMENT] Direction RA(deg.) 28.518543 DEC 89.600030 TDV(x 0.006134 y -0.003333 z 0.999976) "
"[ALIGNMENT] Failed TransformTelescopeToCelestial: Scope RA=8.48613 Scope DE=89.600030, Aligned RA=8.486128 DE=89.600030 "
"[COMM] dispatch_command: \":f1\", 4 bytes written "
"[COMM] read_eqmod: \"=101\", 5 bytes read "
"[COMM] dispatch_command: \":f2\", 4 bytes written "
"[COMM] read_eqmod: \"=311\", 5 bytes read " <----------- response = motor 2 (Dec): low-speed, reverse, slew-mode, running, initialized
"[SCOPE] GetRAPeriod() = 9 "
"[SCOPE] GetDEPeriod() = 289 "
"[DEBUG] StopDE() : calling DE StopWaitMotor "
"[COMM] dispatch_command: \":f2\", 4 bytes written "
"[COMM] read_eqmod: \"=311\", 5 bytes read " <------------ same response continues as long as motor is moving
"[MOUNT] StopWaitMotor() : Axis = 2 "
"[COMM] dispatch_command: \":K2\", 4 bytes written "
"[COMM] read_eqmod: \"=\", 2 bytes read "
"[COMM] dispatch_command: \":f2\", 4 bytes written "
"[COMM] read_eqmod: \"=311\", 5 bytes read " <------------ same response
"[COMM] dispatch_command: \":f2\", 4 bytes written "
"[COMM] read_eqmod: \"=311\", 5 bytes read " <------------ same response
"[COMM] dispatch_command: \":f2\", 4 bytes written "
"[COMM] read_eqmod: \"=301\", 5 bytes read " <------------ motor has stopped moving
Second Nudge:
"[MOUNT] StartMotor() : Axis = 2 "
"[COMM] dispatch_command: \":J2\", 4 bytes written "
"[COMM] read_eqmod: \"=\", 2 bytes read "
"[SCOPE] Compute local time: lst=10.38794952 (10:23:16.62) - julian date=2458362.30806703 "
"[COMM] dispatch_command: \":j1\", 4 bytes written "
"[COMM] read_eqmod: \"=E4377A\", 8 bytes read "
"[SCOPE] GetRAEncoder() = 8009700 "
"[COMM] dispatch_command: \":j2\", 4 bytes written "
"[COMM] read_eqmod: \"=FF3F84\", 8 bytes read "
"[SCOPE] GetDEEncoder() = 8667135 "
"[SCOPE] Current encoders RA=8009700 DE=8667135 "
"[ALIGNMENT] Status: Mnt. Algnt. NORTH Date 2458362.308067 encoders RA=8009700 DE=8667135 Telescope RA 8.486713 DEC 89.612687 "
"[ALIGNMENT] Direction RA(deg.) 28.518543 DEC 89.612687 TDV(x 0.005940 y -0.003227 z 0.999977) "
"[ALIGNMENT] Failed TransformTelescopeToCelestial: Scope RA=8.48671 Scope DE=89.612687, Aligned RA=8.486713 DE=89.612687 "
"[COMM] dispatch_command: \":f1\", 4 bytes written "
"[COMM] read_eqmod: \"=101\", 5 bytes read "
"[COMM] dispatch_command: \":f2\", 4 bytes written " <---------- first query of Dec motor status
"[COMM] read_eqmod: \"=701\", 5 bytes read ": <---------- status: high-speed, reverse, slew-mode, stopped, initialized
I tested changing "GVal" to 1 when stopping the motors and it fixed the problem, though I'm not sure if it will affect any other functionality.
Entire Second Nudge after fix:
"[DEBUG] SlewDE() : rate = 4 "
"[DEBUG] Slewing DE at 4.00 4.00 121 144.867900 "
"[MOUNT] SetMotion() : Axis = 2 -- dir=forward mode=slew speedmode=lowspeed "
"[SCOPE] CheckMotorStatus() : Axis = 2 "
"[MOUNT] SetSpeed() : Axis = 2 -- period=289 "
"[COMM] dispatch_command: \":f2\", 4 bytes written "
"[COMM] read_eqmod: \"=101\", 5 bytes read "
"[COMM] dispatch_command: \":I2210100\", 10 bytes written "
"[COMM] read_eqmod: \"=\", 2 bytes read "
"[MOUNT] StartMotor() : Axis = 2 "
"[COMM] dispatch_command: \":J2\", 4 bytes written "
"[COMM] read_eqmod: \"=\", 2 bytes read "
"[SCOPE] Compute local time: lst=17.15791077 (17:09:28.48) - julian date=2458362.58937856 "
"[COMM] dispatch_command: \":j1\", 4 bytes written "
"[COMM] read_eqmod: \"=E4377A\", 8 bytes read "
"[SCOPE] GetRAEncoder() = 8009700 "
"[COMM] dispatch_command: \":j2\", 4 bytes written "
"[COMM] read_eqmod: \"=BE4084\", 8 bytes read "
"[SCOPE] GetDEEncoder() = 8667326 "
"[SCOPE] Current encoders RA=8009700 DE=8667326 "
"[ALIGNMENT] Status: Mnt. Algnt. NORTH Date 2458362.589379 encoders RA=8009700 DE=8667326 Telescope RA 15.256675 DEC 89.550703 "
"[ALIGNMENT] Direction RA(deg.) 28.518543 DEC 89.550703 TDV(x 0.006890 y -0.003744 z 0.999969) "
"[ALIGNMENT] Failed TransformTelescopeToCelestial: Scope RA=15.2567 Scope DE=89.550703, Aligned RA=15.256675 DE=89.550703 "
"[COMM] dispatch_command: \":f1\", 4 bytes written "
"[COMM] read_eqmod: \"=101\", 5 bytes read "
"[COMM] dispatch_command: \":f2\", 4 bytes written "
"[COMM] read_eqmod: \"=111\", 5 bytes read " <------------ Motor 2 (Dec): low-speed, forward, slew-mode, running, initialized WOOOOO!!!
"[SCOPE] GetRAPeriod() = 9 "
"[SCOPE] GetDEPeriod() = 289 "
"[DEBUG] StopDE() : calling DE StopWaitMotor "
"[COMM] dispatch_command: \":f2\", 4 bytes written "
"[COMM] read_eqmod: \"=111\", 5 bytes read "
"[MOUNT] StopWaitMotor() : Axis = 2 "
"[COMM] dispatch_command: \":K2\", 4 bytes written "
"[COMM] read_eqmod: \"=\", 2 bytes read "
"[COMM] dispatch_command: \":f2\", 4 bytes written "
"[COMM] read_eqmod: \"=111\", 5 bytes read "
"[COMM] dispatch_command: \":f2\", 4 bytes written "
"[COMM] read_eqmod: \"=111\", 5 bytes read "
"[COMM] dispatch_command: \":f2\", 4 bytes written "
"[COMM] read_eqmod: \"=101\", 5 bytes read "
I have forked your github repo and submitted a pull request containing the changes.