You reached the limit. On step one of the publication editor the title stops at 200 characters and the description at 500. Both are enforced by the field itself, so typing simply stops working and a paste is cut to fit. There is no counter, no colour change and no message, which is why it reads as the page having frozen.
Nothing is trimmed later. What the field will hold is exactly what gets saved.
Neither field is the place for the long version
Both are short on purpose. The title is the line on your publication card and in search results. The description is the paragraph beneath it, and it is what a reader decides on before opening anything.
If the writing you are trying to fit is an abstract, a credit list or a chapter summary, it belongs inside the PDF. A reader who wants that detail is one click away from it, and the PDF has no limit.
Both feed your publication's web address
This is the part that catches people. The address of a published publication is built from your title and your description together, cut to the first 40 characters. So editing the description of something you have already published is not a cosmetic change: it can move the publication to a different address and break links you have shared.
Decide on both before you publish, and treat later edits to either as a decision about the link.
Links in the description do not survive
A URL typed into the description is stripped when it saves, and it is not recoverable afterwards. Put the link inside the PDF, or in the publication's own metadata on step two.