But now I encounted another issue, after changing the slit several times, my chromatograms showed some wavy patterns,
it could show up in the middle of the run.
I doubt it is the detector malfunction.
It's easy to tell: just set the slit width back to its initial value and see if the problem goes away. That said, I agree that it is unlikely to be a detector issue; more likely to be air bubbles or a sticking check valve. The intermittent nature really makes air bubbles the most likely suspect.
The wavy patterns happened no matter what method I used.
patterns change all the time and seem erratic.
Fortunately, after several rounds of restarting the detector, it self-healed.