This thread is talking about something very serious in Web SDK. I think everyone who is using Web SDK do have this problem. (If not, you will face it in near future)
I would say this is a BUG in Web SDK. 
I do not see the fix for this bug in future development road map for Web SDK. Why is that? 
@tommy Your last response doesn’t make sense. We do not want to use Zoom App. OP has already mentioned about it and we clearly do not want to redirect our users to zoom application. If you encourage to do so, I’m just wondering what is the purpose of Web SDK at all? 
I assume whether the video lag is because Web SDK do not have buffering mechanism which causes video cut-offs? (I didn’t look into the Web SDK source code, I’m just assuming)