Flickering in OBS, fine in VLC

[uzer123]

I digitize some VHS tapes. I have an RCA to HDMI adaptor, and another Video capture device that takes the HDMI to output to USB, which i put in my pc.
Everything goes fine, but i have very often flickering like every 1-5 seconds. Log is like this:

16:36:17.711: warning: Found EOI before any SOF, ignoring
16:36:17.711: fatal: No JPEG data found in image
16:36:17.711: Video Capture Device: Error decoding video
16:36:17.743: warning: Found EOI before any SOF, ignoring
16:36:17.743: fatal: No JPEG data found in image
16:36:17.743: Video Capture Device: Error decoding video
16:36:17.775: warning: Found EOI before any SOF, ignoring
16:36:17.775: fatal: No JPEG data found in image
16:36:17.775: Video Capture Device: Error decoding video
16:36:17.807: warning: Found EOI before any SOF, ignoring
16:36:17.807: fatal: No JPEG data found in image
16:36:17.807: Video Capture Device: Error decoding video
16:36:17.840: warning: Found EOI before any SOF, ignoring
16:36:17.840: fatal: No JPEG data found in image
16:36:17.840: Video Capture Device: Error decoding video
16:36:17.845: warning: mjpeg_decode_dc: bad vlc: 0:0 (0000018E6F5FC988)
16:36:17.845: error: error dc
16:36:17.845: error: error y=134 x=58
16:36:17.871: warning: Found EOI before any SOF, ignoring
16:36:17.871: fatal: No JPEG data found in image

I've tried different cables, usb ports etc. but nothing solves that. What is strange though, is if a play the video with VLC as Capture Device, the video is playing perfect. So, it doesnt look like a hardware problem.

Both VLC and OBS are updated.