Regression with ExtendedUpgrades OnRestore vscript output causes overflowed reliable buffer

[amagnemite]

I have this OnRestore block in an extendedupgrade:

OnRestore {
 Output "!activator,$VScriptFunc$levelCheck,,0"
}

Previously, it worked fine. Recently however, the presence of this block causes everyone to be kicked with the message "[x] overflowed reliable buffer" whenever the map reloads. It appears be specific to vscript funcs, as Output "!activator,$displaytextchat,restore,0" does not appear to cause an overflow.