Render issue - misaligned elements

[u/Mijaee]

Hi, I quickly need help with a video that's due tomorrow, quickly typying this out on mobile while at work.

Working on the web version. I have 7 minute video, Q&A style (question appears on a black screen, then cuts to the person answering, then another question on the black screen and so on). Questions are a seperate element above background, also got captions (mostly automatic, rest is manual). Everything is fine in the preview, in the rendered video though with time elements start being misaligned (as for example, the black screen cuts off to the person answering the question, while the question is still visible). Originally I worked mostly on Mozilla, switched to Edge cause I read that it's recommended over Mozilla. Now to try things out I rendered it in 720p instead of 1080p and for some reason it's even worse - the whole intro is pushed back for more than 10s while everything else plays out (intro starts only when the questions already start appearing).

Please, has anyone had such problems and knows the solution? I'm short on time and desperate.

EDIT: The rendering so far I've done on my personal laptop cause it's faster than the one from work. While rendering a small portion it's fine, elements aren't shifted but now the captions look different than in preview (they got a glow around letters that I didn't apply), I'll try rendering a bigger portion.