K1 max Missed scheduling of next digital out event

Everything was printing ok, went to print again now I get this error
Missed scheduling of next digital out event This is generally indicative of an intermittent communication failure between micro-controller and host.

klipper error
!! {“code”: “”, “msg”:"MCU ‘mcu’ shutdown: Missed scheduling of next digital out event

is there an odd character in the filename that gets the gcode confused? Something like an apostrophe?