So I've used external intervalometers for years with my T series and 70D bodies but having an issue with the R5.  The external intervalometer works the same as previous ones but just with a different end.  I can set up a run fine, like 4 second shots with a 5 second interval and the external intervalometer seems happy with everything and goes about it's program when I click Start.

The problem is the first exposure opens the shutter but after the 4 seconds isn't ending the exposure and closing the shutter.  The intervalometer goes along it's program unaware the camera never ended that first shot.

Best I'm finding on forums and such in searches is that MAYBE I have a bad (brand new) intervalometer.  Suppose that could be it but wanted to ask if anyone else has run into this behavior before.  TIA!