GL_INVALID_OPERATION from draw call: glGetError returns it once, then GL_NO_ERROR — which command actually failed?
An OpenGL 4.5 core-profile application (desktop, GLFW-created context) renders a scene with several draw calls, VAOs, and shader programs per frame. After a recent change, nothing appears on screen. Polling glGetError once per frame reports GL_INVALID_OPERATION a single time, then returns GL_NO_ERROR on every subsequent call, even though the failure persists