Not sure if this is very helpful other than that it confirms a segfault. What's odd is that it worked the first time.

Looks like gdb is broken on RPI3. Can you repeat it on a desktop/laptop?

I'll give that a try and take notes as I go. Ran out of time tonight so will try tomorrow

I ran indiserver on my x64 Ubuntu VM.
Like on the RPi3 it runs ok until the config file is saved from Ekos. Then it wont start ever again. Attaching the output from gdb (only marginally more helpful than on the RPi3) plus indi and kstars logs. I can view the indi logs in the VM but attempts to copy them result in a "protocol error" and I cannot extract or view anywhere else.
I cannot connect to the driver because it crashes before the listener starts up.

Acting on a hunch I renamed the Optec TCFS config file to effectively disable it. After that I renamed it back and the driver failed so the issue is related to reading the config file.
Attaching the offending file (with .txt extension added to keep the forum software happy) just in case it helps

The GDB file is more useful now but you didn't type in bt when you got the crash. You need in to type that to get the full backtrace. I tried to use the same config here but it didn't crash with the TCF-S simulator. So try gdb again and try to get the full backtrace.

At least now I can reproduce the error at will. Attaching gdb backtrace

Ok, the gdb is still not very useful to indicate the exact issue. At any rate, I updated the driver, so check again after tomorrow's update.

I built libindi on the VM and TCFS driver no longer crashes. However, it seems to have problems processing commands.
Kstars and Indi logs attached.
BTW - is it possible to change INDI log filenames to change ":" to some other character? Windows can't open the files when it contains ":"

You don't need to submit two files now. Just the KStars one is enough since it also logs the driver (if you check Focuser logging which you did). I will check it out.

Ok driver updated again, please re-test.

Still getting errors with the "Unrecognized error code"
Not able to disconnect except by closing down Kstars