This may be related to 'Stop answering close-worthy questions!', but I think it is sufficiently different to be asked separately.
A few times I have researched and answered a question, but when I go to press the 'Post your answer' button it is greyed out. I then notice that there is a yellow banner at the top of the page indicating that the question has been placed on hold. The banner was not there when I started to answer the question, so the question was placed on hold while I was answering. Because I am focusing on the bottom half of the monitor, I did not notice a change at the top. The inability to post an answer is quite annoying, as anything from 10 minutes to an hour of research and writing time is totally wasted. (OK, I accept that I learned something new, so the time was not 'totally wasted', but I still feel my effort has been devalued.)
Sometimes, before preparing an answer, I can see someone has indicated that the question has problems, (e.g. They may indicate that the question is a duplicate of an earlier question.) This leaves me in a quandary, should I start to prepare an answer or not.
If the question is subsequently closed, preparing an answer will be a waste of time. If the question is not closed and the question may not be answered, because other potential responders are also scared off, and the OP may not get an answer when one is available.
I usually try to resolve this issue by clicking on the links provided by the person who thought the question should be closed. If I agree with them, then I will skip that question and assume it will be closed. However, sometimes I will disagree that the question should be closed, For example, I may agree that the question is similar to a previous question but think that it is sufficiently different as to justify it not being closed. What should I do then? I usually start to provide an answer, hoping it will not be closed before I am finished.
I would like to tentatively suggest the following, as a step towards solving this issue. I am not a programmer, nor am I sufficiently aware regarding the systems used by SE to know if this is even possible.
If someone has started to answer a question, before it is closed, then they should be able to post that answer.
If the question is closed before the answer is posted, then no points will be awarded.
If the question is subsequently re-opened, the points will be awarded. (I don't really care if they are or not, but I expect that there would be some people who do.)
The OP will not be notified that an answer has been provided unless the question is re-opened.
As at present, no-one can start to answer a question after it has been closed.