chengel The Set Guiding Rate … command does not appear to have any effect at all.
Many programs are using the generic LX200 Autostar instruction set to control the ZWO mount. The original lx200 instruction set does not have a "set guide rate" command, and depends on the hand controller to set that.
When I checked the driver in INDIGO, it had added a special case for the ZWO mount in its lx200 driver, by appending a number to the LX200's "select guide rate" command, that not only selects the guide rate but also sets the actual rate.
I do not see such a special case for the INDI and ASCOM lx200 drivers over at Github. ZWO needs to check out those open sourced drivers and apply the needed code. From the computer engineering aspect, ideally, setting and selecting should really be two separate commands -- conflating the two would just lead to problems in the future.
That is the first place to check, i.e. whether the program is compatible with the instructions that the mount expects.
FWIW, even the INDIGO driver appears to have a small bug when setting the guide rate. I have already alerted Peter about it to have him take a look; I don't usually delve in low level code to know for sure. It won't help you though, since ASCOM does not go through INDIGO.
Chen