There is some bug with shader and the stock viewer in 1.19.3. We can see the bar with some shader, and with other it's a light beamn 1.19.3. We can see the bar with some shader, and with other it's a light beam.

Similar problem with Complementary Shaders reimagined 1.19.2 | Stock viewer flickers, though I realize you can't see the flickering through a screenshot

Here's another screenshot to better demonstrate the flickering

@SmallishMink34 Could you help me to understand how to add stock viewer to shop item? I can test with my shaders then also in 1.19.3.

Vanilla:

Complementary shaders:

Insanity shaders:

Same problem
Shader Astralex
MC 1.19.2