intervalometer stopping before all shots were taken

[Matikr]

with covid19 put a hold on all my plans for night photography for the past couple of months, I'm about to head out to try some today, but for the life of me I can't understand why would my camera stop taking pictures before the amount I set for it.

for ex,  I set it to stop after 120 shots of 30sec, but I only got 90 pic or so..
 
Camera is connected to a powerbank (still full), and camera power saving modes is set to "disabled" so neither the camera or the power bank are going into sleep mode

more info-
intervalometer setting:

Take a pic every - "shoot like crazy" (so I don't have big gaps in the star trails
Start trigger - "Leave manu"
Start After - 10s
Stop after - 120 shots
Camera setting:
Shooting drive =continuous shooting
Image review = off

don't know if anything else I'm doing might be the cause of this?

Thank in advance!

[Levas]

Maybe you have the option 'long exposure noise reduction' enabled in camera (Canon menu) ?
If that option is enabled, the camera automatically takes another picture after one is taken, with the same exposure time, but without openening the shutter (it takes a blackframe and substracts it from the actual picture).
Since it's done automatically and initiated by Canon software, maybe that messes it up 

[Matikr]

Thanks. Noise reduction is off, and the camera takes shot after shot perfectly with only 1sec between images, but it just stops after a while, and before it hits the amount of shots i  set for it

[c_joerg]

and the camera takes shot after shot perfectly with only 1sec between images,

I think that’s the problem. 1s between images is not always enough. You should compare all EXIF timestamps from your images. May be the first and last is enough.

Not sure if this problem still happens
https://www.magiclantern.fm/forum/index.php?topic=21617.msg203896#msg203896

[Matikr]

so wanted to report back on the subject.
I don't know why, but if I set the camera to Bulb mode and shoot 1min long exposures, everything is fine. If I set it up to shoot at the camera's max shutter speed (30") then it stops shooting even if it didn't reach the amount of frames I set it up to shoot.

either way I find that for star trails, 1 min frames works better - less ISO noise, but not too long long of an exposure to show sensor noise or that purple stains in the edges of the frame.