I think we may have stumbled onto the cause.
We have four ASP searches. Two are constrained to 200px width. Two were set to default width (no width specified) which resulted in 100% width. Before the recent ASP updates, the widths of the different ASP searches were respected. After the update, the width of the 200px search appears to have been set globally via .asp_w_container{width:200px}, causing all four ASP searches to be constrained to 200px.
I’m guessing the old code properly constrained the CSS settings to each ASP search, but the new code inadvertently broke the constraints. The way to test would be to create a site/page with multiple searches, set to different sizes.