First midi notes in looped bar very jittery in Cubase 13

The first note of a looped bar is very jittery and different on different midi ports.

Steps to reproduce.

1: Create an empty project.

2: Create a one bar part with four notes, one on each beat, one 16th in duration. The first note should be right at the start of the bar.

3: Send this track to external hardware drum machine. i.e, rimshot.

3: Copy the part to another track. This track should go to another drum machine with a separate dedicated port on the midi interface.

4: Loop the bar, and listen. The timing of the first rimshot will be different on both drum machines (up to 40ms jitter). The subsequent three notes will have the same timing. (At least as close as hardware midi gets anyway.)

5: Save the project, then open the same project in Cubase 6.5, and observe that the timing is now correct without the large jitter on the first note.

My Rig: Cubase 13, Two ESI M8U EX midi interfaces and one ESI M8U XL. Both EX in USB 2 mode with running status, using WinRT mode in Cubase. Sound Card: Motu M4.

The computer is used just for hardware midi, and recording a single stereo track. It is running Windows 10 has only the most minimal Cubase 13 (No additional plugins or any VST instruments) and Cubase 6.5 installed.