This is like the second time it happens and I lose almost an entire night's worth of work. Doesn't seem to be caused by anything, just happens at random. Here's the log if it helps:
2023-02-22T22:28:00 Capturing 300,000-second image...
2023-02-22T22:27:55 Captured /home/ovidiu/captures/horsehead4/Light/horsehead4_Light_062.cr2
2023-02-22T22:27:55 Received image 13 out of 200.
2023-02-22T22:27:55 Download Time: 4.37 s, New Download Time Estimate: 4.41 s.
2023-02-22T22:22:49 Capturing 300,000-second image...
2023-02-22T22:22:49 Job requires 300,000-second images, has 12/200 frames captured and will be processed.
2023-02-22T22:20:58 CCD capture aborted
2023-02-22T22:20:37 Capturing 300,000-second image...
2023-02-22T22:20:37 Dither complete.
2023-02-22T22:20:37 Dithering succeeded.
2023-02-22T22:19:45 Dithering...
2023-02-22T22:19:45 Captured /home/ovidiu/captures/horsehead4/Light/horsehead4_Light_062.cr2
2023-02-22T22:19:45 Received image 12 out of 200.
2023-02-22T22:19:45 Download Time: 4.28 s, New Download Time Estimate: 4.41 s.
2023-02-22T22:14:39 Capturing 300,000-second image...
2023-02-22T22:14:34 Captured /home/ovidiu/captures/horsehead4/Light/horsehead4_Light_062.cr2
2023-02-22T22:14:34 Received image 11 out of 200.
2023-02-22T22:14:34 Download Time: 4.36 s, New Download Time Estimate: 4.42 s.
2023-02-22T22:09:29 Capturing 300,000-second image...
2023-02-22T22:09:28 Dither complete.
2023-02-22T22:09:28 Dithering succeeded.
2023-02-22T22:08:54 Dithering...
2023-02-22T22:08:54 Captured /home/ovidiu/captures/horsehead4/Light/horsehead4_Light_062.cr2
2023-02-22T22:08:54 Received image 10 out of 200.
2023-02-22T22:08:54 Sequence resumed.
2023-02-22T22:08:43 Sequence paused.
2023-02-22T22:08:43 Download Time: 4.24 s, New Download Time Estimate: 4.43 s.
2023-02-22T22:07:55 Sequence shall be paused after current exposure is complete.
2023-02-22T22:03:37 Capturing 300,000-second image...
2023-02-22T22:03:32 Captured /home/ovidiu/captures/horsehead4/Light/horsehead4_Light_062.cr2
2023-02-22T22:03:32 Received image 9 out of 200.
2023-02-22T22:03:32 Download Time: 4.38 s, New Download Time Estimate: 4.45 s.
2023-02-22T21:58:27 Capturing 300,000-second image...
2023-02-22T21:58:26 Dither complete.
2023-02-22T21:58:26 Dithering succeeded.
2023-02-22T21:57:33 Dithering...
2023-02-22T21:57:33 Captured /home/ovidiu/captures/horsehead4/Light/horsehead4_Light_062.cr2
2023-02-22T21:57:33 Received image 8 out of 200.
2023-02-22T21:57:33 Download Time: 4.24 s, New Download Time Estimate: 4.46 s.
2023-02-22T21:52:28 Capturing 300,000-second image...
2023-02-22T21:52:23 Captured /home/ovidiu/captures/horsehead4/Light/horsehead4_Light_062.cr2
2023-02-22T21:52:23 Received image 7 out of 200.
2023-02-22T21:52:23 Download Time: 4.21 s, New Download Time Estimate: 4.49 s.
2023-02-22T21:47:18 Capturing 300,000-second image...
2023-02-22T21:47:18 Dither complete.
2023-02-22T21:47:18 Dithering succeeded.
2023-02-22T21:46:50 Dithering...
2023-02-22T21:46:50 Captured /home/ovidiu/captures/horsehead4/Light/horsehead4_Light_062.cr2
2023-02-22T21:46:50 Received image 6 out of 200.
2023-02-22T21:46:50 Download Time: 4.47 s, New Download Time Estimate: 4.54 s.
2023-02-22T21:41:45 Capturing 300,000-second image...
2023-02-22T21:41:40 Captured /home/ovidiu/captures/horsehead4/Light/horsehead4_Light_062.cr2
2023-02-22T21:41:40 Received image 5 out of 200.
2023-02-22T21:41:40 Download Time: 4.42 s, New Download Time Estimate: 4.55 s.
2023-02-22T21:36:34 Capturing 300,000-second image...
2023-02-22T21:36:34 Dither complete.
2023-02-22T21:36:34 Dithering succeeded.
2023-02-22T21:35:50 Dithering...
2023-02-22T21:35:50 Captured /home/ovidiu/captures/horsehead4/Light/horsehead4_Light_062.cr2
2023-02-22T21:35:50 Received image 4 out of 200.
2023-02-22T21:35:50 Download Time: 4.52 s, New Download Time Estimate: 4.59 s.
2023-02-22T21:30:44 Capturing 300,000-second image...
2023-02-22T21:30:39 Captured /home/ovidiu/captures/horsehead4/Light/horsehead4_Light_062.cr2
2023-02-22T21:30:39 Received image 3 out of 200.
2023-02-22T21:30:39 Download Time: 4.29 s, New Download Time Estimate: 4.61 s.
2023-02-22T21:25:33 Capturing 300,000-second image...
2023-02-22T21:25:33 Job requires 300,000-second images, has 2/200 frames captured and will be processed.
2023-02-22T21:20:55 CCD capture aborted
2023-02-22T21:20:55 Autoguiding stopped. Aborting...
2023-02-22T21:19:47 Capturing 300,000-second image...
2023-02-22T21:19:47 Job requires 300,000-second images, has 2/200 frames captured and will be processed.
2023-02-22T21:10:20 CCD capture aborted
2023-02-22T21:10:20 Autoguiding stopped. Aborting...
2023-02-22T21:09:59 Capturing 300,000-second image...
2023-02-22T21:09:54 Captured /home/ovidiu/captures/horsehead4/Light/horsehead4_Light_064.cr2
2023-02-22T21:09:54 Received image 2 out of 200.
2023-02-22T21:09:54 Download Time: 5.10 s, New Download Time Estimate: 4.77 s.
2023-02-22T21:04:48 Capturing 300,000-second image...
2023-02-22T21:04:43 Captured /home/ovidiu/captures/horsehead4/Light/horsehead4_Light_063.cr2
2023-02-22T21:04:43 Received image 1 out of 200.
2023-02-22T21:04:43 Download Time: 4.44 s, New Download Time Estimate: 4.44 s.
2023-02-22T20:59:37 Capturing 300,000-second image...
2023-02-22T20:59:37 Job requires 300,000-second images, has 0/200 frames captured and will be processed.

Ovidiu,

This is a known issue that has been raised multiple times but as far, as I am aware, never resolved.

The work around is to append the time to each file, which is an option on the capture screen.

Paul

What version of KStars is this? No way to reproduce it at all?

Kstars version 3.6.3 Stable. I don't know if this is what caused it but I manually stopped and restarted the capture before the issue arose.