ExtendScript: No longer able to add effects using QE DOM

I'm trying to add an effect to a Clip in my Sequence using this code in my CEP panel using addVideoEffect, as in this thread. However, when I run this code to get the Clip:

qeClip = qe.project.getActiveSequence().getVideoTrackAt(0).getItemAt(0);

it gives me an error that says "Object is invalid."

This call is working fine in Premiere v 13.1.5, but not in Premiere 14.3 or 14.3.1. The problem seems to be with the call .getItemAt(0). If I omit that and just return the first video track, I'm able to get the track's numItems and other properties... but when I try accessing any of the qeClip's properties, like qeClip.start.frames, or any of its methods, I get the "Object is invalid" error even though that works in an older version of Premiere on my machine. This is preventing me from making a call to the addVideoEffect method, which from my understanding is the only way to add an effect to a clip using ExtendScript.

I understand that the QE DOM is officially unsupported, but is there a workaround for this? Is there another way for me to return a desired clip from my Sequence using the QE DOM, so that I can add an effect to it? If not, is there any other way to add an effect to a clip?

Thanks.