Yeah, unfortunately a number of quarks override core functionality in a way that breaks it. It’s not an uncommon problem, alas. See e.g. autogui. One issue for quark writers is that SC class lib doesn’t always provide enough hooks so that less brutal methods than overrides can be employed.
I’m not sure it’s override problem here though. I can see from the stack trace that CmdPeriod:run calls ScinServer:cmdPeriod but that may have been just a regularly hooked callback with CmdPeriod.add. Maybe CmdPeriod should be more tolerant of errors in these, i.e. try { } them, but that might lead to
other issues like unreported errors. The correct solution is probably for ScinServer:cmdPeriod to inspect the kind of object it tries to do its work on, i.e. the try { } should probably be at ScinServer:cmdPeriod level.
You should probably report this as a bug in Scintillator. Maybe its author still maintains that quark and will fix it. It looks like it had activity in the past year. Actually, it’s the latest issue reported against it 
as of this time
Which actually points back to a fix here: