(Please forgive me if I am not using proper carpentry terms)
I recently noticed I have a vertical wood frame popped out. I am suspecting it is caused by thermal expansion. I can see these are vertical frame joined by sectioned wood. I am living in Seattle so a bit worried about moisture intrusion to cause more damage.
I tried to use a hammer to put it into the slot but it barely moved at all.
Is it common for it to be popping out? Could it be caused by structural issues or just thermal expansion?
How to fix it since hammer isn't quite helping? I don't think nail is a good idea because there is no nail at all on the trim.